No need to fill your backpack with expensive and unreliable tools. With these best 100 online calculators and conversion resources, you can do many common and uncommon tasks such as mathematics, graphing, finance, health, science, conversions, and even have some fun.

Best Online Calculating Sites

Stop here for extensive lists of online calculators. They are all available for free and are as easy to use as clicking a mouse.

1. Math.com: The world of math online, this site has converters, equation solvers, and graphers in addition to calculators. Get dozens of different online calculators for free, or get help with homework, cool tools, study tips, and more.

2. Calculate For Free: This site has a drop down menu to give you every calculator from accident reconstruction to zodiac. You can also get resources for finance, weight loss, loans, and more.

3. Martindale’s Calculators On-Line Center: The site currently contains over 23,730 calculators and spreadsheets. Choose from subjects such as agriculture, math, science, and more to get dozens of online calculators.

4. Calculator.com: Some of the more popular choices on this site include mortgage, currency, time, love, and area calculator. They even offer calculators for various internet ready devices.

5. CalcEnstein: With new calculators added all the time, this site is worth a look for its friendly layout. Get calculators for a variety of subjects, or run a Google like search.

6. The Calculator Home Page: Several popular calculators are listed here including javascript, unit conversions, loan, currency, and more.

7. WebCalc: The calculator menu on this site shows you all of their available resources. You can also join the forums or sign up for their newsletter.

8. Bloomberg: A leading finance site, they have dozens of free, online calculators to choose from. You can get one in categories such as auto, investment, mortgage, savings, and loans.

Best Online Finance Calculators

Because science is good for money too, check out these free calculators to make the most of your finances.

9. Debt vs. Savings Calculator: Wondering if paying off that debt will save you more than putting money in the bank? Then use this free tool to input both and get detailed results along with help.

10. Debt-Free Calculator: Provided by CNNMoney, this calculator tells you when you will be debt free from multiple or single credit cards. There is also a reverse calculator that can tell you how much to pay to be debt free by a certain time.

11. Net Worth Calculator: Want to know how much you are actually worth? Then type in your assets and liabilities to get the truth and you can even save the results.

12. Credit Card Menu: They can destroy finances, but everyone needs them, so find out which is best for you by using this side by side comparison of many popular cards. You can also choose by categories such as student cards, low APR, balance transfer, and rewards cards.

13. Loan Calculator: Want to know the bottom line on a loan without having to contact an outside source? Then input loan amount, interest rate, date, and term to know your monthly payments instantly. You can also get a calculator to help you see how much extra payments can save you.

14. Cost of Borrowing from 401(k) Calculator: See the advantages and disadvantages of this risky move by using this free, online calculator. Type in your current balance, estimated rate return, monthly contributions, loan amount, interest, period, and monthly payoff amounts to see if this is truly a good idea.

15. Roth vs. Traditional IRA Calculator: Want to know which is right for you without having to call a brokerage house? Then type your information into this simple calculator to get an instant result.

16. Adjustable vs. Fixed Mortgage Calculator: See how a steady mortgage payment differs from one that varies with this free tool. Answer a series of simple questions to get the results.

17. Spending Plan Calculator: Don’t know how much you are spending or should be spending? Then type in your gross income to get an instant budget on an array of items such as housing, auto, insurance, savings, investments, and more.

18. Retirement Planner: CNNMoney helps you estimate how well your savings program is preparing you for retirement. Answer questions on your goals, income, savings, and portfolio to get your results.

Best Social Security Calculators

Use these government sponsored tools to estimate your Social Security benefits. They are also available in Spanish.

19. Quick Calculator: This calculator gives you a simple, rough estimate when you input your date of birth and this year’s earnings. You must be at least 22 and answers come in today’s or inflated dollars.

20. Online Calculator: Input your date of birth and your complete earnings history to get a benefit estimate. More lengthy than the one above, you can get a more detailed estimate of benefits.

21. Online WEP Calculator : This calculator is intended for those who will receive pension on retirement. Learn more about who should use this calculator and the Windfall Elimination Provision.

22. Government Pension Offset Calculator: If you receive a pension from a government job in which you did not pay Social Security taxes, some or all of your benefits may be offset. In addition to the calculator, there is also more information on who is exempt from this.

23. Detailed Calculator: This one must be downloaded and is compatible with Windows or Mac. It includes many specialty features not available on the above and comes with a user’s guide.

24. Retirement Estimator: Those who qualify for Social Security benefits but are not yet receiving them and under the age of 62 can use this free tool. Benefit estimates are based on your actual Social Security earnings record.

Best Free Downloadable Calculators

Stay offline and on task by downloading these calculator programs at no charge.

25. Calc: Over 2 million visitors have used the Calc software available for PC or handheld devices. There is a free or for purchase option, and you can get more information on using this for Mac.

26. Moffsoft: Windows users can download this free calculator to replace their current one. You can also download the Calculator 2 for a more powerful calculator with many other features.

27. HiDigit: This essential and powerful program works best for math and engineering students, along with their teachers. Available for Windows, you can download for free or purchase for $19.95.

28. Calc98: In addition to doing simple arithmetic, Calc98 supports many financial functions. You can also use it for unit conversions, physical constants, and support for matrices and complex numbers.

29. Graphing Calculator 3D: Plot high quality graphs for 2D and 3D functions and coordinates tables with this software. Both cartesian and polar coordinates are supported as well as parametric equations and inequalities.

Best Calculators for Firefox

Add these free tools to your browser to get more done without having to open new programs.

30. Status-bar Scientific Calculator 4.5: This tiny calculator is added to your status bar and you can quickly click on it to expand. It has four different modes to perform a variety of tasks.

31. Status-bar Calculator: Similar to the above, it is a simpler version of a calculator. It does simple math and decimal/octal/binary conversions.

32. Calculator 1.1.12: With an interface similar to Microsoft Powertoy Calculator, it offers great features like history, conversions, and many functions. It also is available in 17 different languages.

33. Graphing Calculator Toolbar: Enter up to five equations into this toolbar, then view the graphs using Firefox native SVG support. It also does arithmetic.

34. Fire Cal: This add on is intended to be a comprehensive calculator suite. It features BMI, exchange rates, compound interest, a high precision math function, and more calculators.

Best Calculators for Windows

Stop here to see or download these free calculators designed especially by or for Microsoft.

35. Pwer Toys: An upgrade to Windows, you can get a bigger and better calculator that does graphs and conversions. You also get other Windows upgrades such as a CD Slide Show Generator, Webcam Timershot, and Virtual Desktop Manager.

36. Currency Converter: An Internet Explorer add on, you can select a currency from any web page you visit. With a simple click you can have it converted to the currency of your choice.

37. Convert Currency to USD With Google: This application is similar to the above and only converts to U.S. dollars. It uses Google’s currency conversion to get the results.

Best Downloadable Calculators for Mac

Although some are also available for PC, these calculators and conversion tools are compatible with Apple.

38. eCalc: Download these easy to use calculators for Windows or Mac. You get eight different ones including trigonometry, scientific, equation solver, and more.

39. Mjograph: This is ideal for those whose works include computer simulations and visualization of their numerical results. It is free to download and features drag and drop data, simple drawing tools, it exports results, and more.

40. Math Type 6.0: This equation editor lets you create mathematical notations for word processing, web pages, desktop publishing, presentations, and for TeX, LaTeX, and MathML documents. Try the demo for free, or purchase the full version.

41. LaTeXiT: Quickly typeset LaTeX equations, without bothering with file creation, and export the image by drag and drop to any application supporting it. Free to download and it comes with many other features.

42. CrystalMaker: Build, display, and manipulate all sorts of crystal and molecular structures in a real time 3D display with this free demo. It supports a wide range of formats and exports high resolution graphics.

43. MConvert: The prime conversion software works with currency, metric and imperial, and currently includes 27 conversion groups and subgroups. They include currency, multi conversion, e=mc2, and many others.

44. Puzzlemaker: Ideal for parents or teachers, use this software to create math puzzles or even crossword puzzles, mazes, and more. There are over 70 samples to motivate you and it comes with a comprehensive teacher’s guide.

Best Conversion Tools

Switch easily between a variety of units by visiting these sites.

45. Online Unit Converter: Get hundreds of online conversion tools with over 2,100 units in 70 categories. You can also get the tool as a download.

46. Online Conversion: Convert just about anything to anything else with the help of this site. Popular conversions include speed, area, fuel economy, currency, and you can also search by category.

47. Metric Conversions: Use these calculators, conversion charts, and tables on a variety of areas to convert to metric. Choose from a variety of categories from acceleration to weight.

48. Lawrence Goetz: Go from standard to metric or vice versa on this site. For use with length, width, weight, volume, temperature, and more.

49. Universal Currency Converter: Perform currency and foreign exchange calculations using live, mid-market rates. This calculator contains the top 85 currencies listing the top 10 first and has more information on currencies.

50. Conversion Calculator: Get all the common conversion units on one site by visiting here. It is also one of the few sites that gives cooking measurement conversions.

51. Morse Code Calculator: Translate any phrase into dots and dashes with the help of this site. You can even get audio playback of your message.

52. Roman Calculator: Want to know what year that movie was made in? Then visit here to get a calculator for not only Roman numerals, but Gregorian and Julian as well.

Best Tools to do Math in Your Head

Think you need a calculator for those heavy tasks? Think again with the help of these leading mathematicians that show you how to turn your head into a powerful adding machine.

53. How to do Math in Your Head – Video: Sean Salazar is a teacher who has posted this free video series on eHow. Fifteen videos show you everything from multiplication, squaring, and beyond.

54. Lazy Maths: Aptly named, this is a leading website featuring a comprehensive collection of speed math shortcuts and smart math techniques. You can learn how to do “zappers,” take a test, and get more information on the “don’t solve” test.

55. Fantastic Math Tricks: Tricks on this site can take just five minutes to learn. They include multiplying any two numbers between one and twenty, the 9x rule, squaring, and more.

56. How to Become a Human Calendar: Calculate the day of the year without consulting a calendar by learning this formula. Once you memorized a few numbers, an easy set of additions and subtractions will have you impressing others in no time.

57. ThemBid: This site shows you five quick math tricks. They include a quick approximation, common percentages, and three others.

58. Vedic Maths: This Indian based math is based on 16 formulas. You can get an easy to follow tutorial on this site, along with related resources.

59. How to do Math in Your Head: James was on a subway when he saw an ad that was betting on readers not being able to do arithmetic in their heads. By solving this problem, he is able to show others how to do the same quickly and easily.

60. Do It In Your Head: If you’re ready to start practicing, visit this site for common questions and various levels of skill. High performers are even listed on the homepage.

61. Short Cut Math: Gerard Kelly brings you this leading book that shows you how to do complex calculations in seconds. Get 150 timesaving math short-cuts for only $3.95.

Best Online Health Calculators and Conversion Tools

Use science and math to help or help predict your own health with these free calculators.

62. Vitality Compass: The Blue Zone brings you four different calculators on life estimations. They include biological age, overall life expectancy, healthy life expectancy, and Blue Zone years.

63. BMI Calculator: Provided by the Mayo Clinic, you can calculate the body mass index for both adults and children. Get results for both standard and metric units, more information on your personal BMI, and other related resources.

64. Calories Burned Calculator: Get an accurate reading on common activities from Health Status. Get options on everything from aerobics to writing, and it even gives a customized report.

65. Male Body Calculator: Who knew wrist size could be this important? Type it in, hit calculate, and get an ideal measurement for chest, waist, biceps, and more.

66. Pregnancy Calculator: The American Pregnancy Association provides a free calculator to help estimate your due date. You can also get many other resources for pregnant women on this site.

Best Periodic Table of Element Tools

The original scientific tool, learn more about the elements, atoms, and even get resources for kids.

67. Dynamic Periodic Table: Brightly colored and well organized, you can get more information on an element simply by scrolling over. You can also customize it in various ways and even get a printout.

68. Interactive Periodic Table: Simply scroll your mouse over an element to get comprehensive information such as melting point, density, % in Earth crust, and more.

69. WebElements: See the entire table in many different versions on this site. You can also choose from compounds, pictures, chemistry, atoms, and more.

70. Chemical Elements: This interactive table can be shown with atomic number, mass, configuration, and other parameters. You can also sort by element groups.

71. Periodic Table of Elements: Visit here if you need the table in French, German, Italian, or Croatian. You can even get three free scientific calculators.

72. The Comic Book Periodic Table of Elements: Learn the elements by linking them to popular superheroes, such as Batman, the Flash, Donald Duck, and others. Developed at the University of Kentucky, this popular table has over two million hits.

73. Los Alamos National Laboratory: This table was designed for elementary, middle, and high school students. The download section features a table for Word, a PDF version, and even a color your own table worksheet.

74. It’s Elemental: Another periodic table for children, it even offers flash cards and other games to help teach. You can also get a useful list of lessons such as how to make an atom model and who discovered each element.

Best Slide Rule Sites

Before electronic calculators, science students relied on this device. Learn about the different types, uses, and more with these sites.

75. Virtual Slide Rule: Use this virtual online tool to see how the basic slide rule works. Learn how to do simple arithmetic, along with interesting facts about the slide rule.

76. Chris Sangwin’s Slide Rule Page: Along with other mathematical instruments, Chris shows you everything about this historic tool. In addition to information on types and uses, there is a download section where you can get cut outs of his favorite slide rules.

77. Eric’s Slide Rule Site: This site contains scans and descriptions of slide rules, along with several pages of useful background information. Get guides such as an introduction, types of slide rules, manuals, where to buy, and more.

78. International Slide Rule Museum: Located in Colorado, this is the world’s largest digital repository of all things concerning slide rules. Get tons of information on this tool including all the major brands, exhibits, and even a How to Use a SR course.

Best Abacus Sites

Another pre-electronic tool, this is how the scientific and mathematic communities did their calculations before the calculator.
79. Online Abacus: A simple and easy to use online tool, use this abacus with the click and drag of a mouse. There are also other fun calculators on this site.

80. Chinese Abacus: Even those who don’t know how to use this will find help on this site. In addition to the abacus, you can get an instruction manual, handbook, history, and more.

81. Virtual Soroban: This is the Japanese version of an abacus. In addition to the online version, you can also get help for using it and a short history.

82. Interactive Abacus Simulator: Running on Java, this simulator is a good way to introduce you to the art of counting beats on a Chinese Abacus. The online tool comes with three easy lessons.

83. Build Your Own Abacus: Intended for grade school science students, this lesson shows you how to build your own abacus using household items. You can also get a background along with related worksheets.

Best Tools for Miscellaneous and Fun Conversions

Unwind from a hectic day of science, and check out these conversions for some laughs.

84. Your Weight on Other Worlds: Find out how much you would weigh on all the planets of the solar system, including Pluto. You can also find out how much you weigh on one of Jupiter’s moons or different types of stars.

85. Chinese Zodiac Sign Calculator: Simply enter your birthday for information on your sign. You can also get more information on the sign, as well as tips for dating.

86. Astrology Chart Calculator: Another “what’s your sign?” site, you can get a detailed personalized chart based on the day, month, and year of your birth. You can also get a horoscope and love calculator.

87. Pig Latin Calculator: Turn any phrase into Pig Latin simply by typing it in one box and hitting translate. You can also view the most emailed messages and get more fun stuff.

88. Blood Alcohol Content Calculator: In four easy questions, you can get an estimated count to see how close to the limit of 0.8% you are. Provided by the Police Department at Oklahoma University, it also comes with the many myths on drinking.

89. Dog Years Calculator: Go beyond the seven year myth to get an actual count of how old you are in dog years and how old your dog is in people years.

90. Lottery Calculator: No better or worse than picking numbers at random, this site has many options to choose from. This free calculator will generate its best picks for various national, regional, and state lotteries.

91. Celebrity Converter: Upload a photo of yourself, hit face recognition, and see which celebrity the computer pulls up. Registration is required.

Best Online Math Games

Stop by these to learn even more math, or just to have some fun.

92. Interactive Mathematics Miscellany and Puzzles: With over 900 games as Java applets, you can find a game for all science students at all levels. Choose from categories such as arithmetic, algebra, visual illusions, and more.

93. Math.com Games: This collection of games is gathered from across the world and includes Fiver, Tower of Hanoi, Virtual Lemonade Stand, and many more. There is also a maze generator that uses Depth-first search, Prim’s algorithm, and Kruskal’s algorithm.

94. Jefferson Lab: Choose from science, math, and element games. There is even a game where 15 questions answered correctly will make you a pretend millionaire.

95. Rubik’s Official Online Site: One of the best and most challenging math games, Rubik’s is now available online. You can find many different and free variations including light speed, eclipse, flat cube, puzzle world, and more.

96. Virtual Rubik’s Cube: Play the original version of this puzzle without ever leaving your computer. If you’re having trouble, view the solution. You can also post a high score or play a multiplayer game.

97. Cool Math Games: Intended for kids, you can find many math games by most popular or editor’s pick. There are also many other math resources on this site.

98. Mathpower: If you like math games and elevator Elvis music, this is the site for you. Most games are aimed at younger science students.

99. The Glossary of Mathematical Mistakes: Technically not a game, but loads of fun for the mistakes made over and over by advertisers, the media, reporters, politicians, activists, and in general many non-math people. View the archives or send in a suggestion of your own.

100. The Diet Problem: The goal of the diet problem is to find the cheapest combination of foods that will satisfy all the daily nutritional requirements of a person. You can get different mathematical formulations of the problem in verbal, basic, mathematical, and AMPL code.

With these 100 top calculators, conversion tools, and tricks, students can complete equations, fix their finances, better their health, teach their children/students, and much more. Be sure to show your favorites to your friends, classmates, and teachers or impress them with a quick trick or two.