Units Converter All tools
Free, no sign-up, nothing stored

Everyday numbers, worked out and explained.

36 calculators and unit converters for cooking, travel, shopping, dates and school math. Each one shows the formula and the steps, so you can check the answer and do it yourself next time.

Browse all tools How we calculate
Exact by definition
1 inch
2.54 cm
1 pound
0.45359237 kg
1 US cup
236.5882365 mL
0 °C
32 °F
1 mile
1.609344 km
1 GiB
1.073741824 GB

These factors are fixed by international agreement, not measured. Our converters use them unrounded.

Five toolboxes

Pick the kind of question you have. Every collection page also explains the ideas behind its tools.

Unit converters

10 tools. Length, weight, volume, temperature, cooking and more, with exact factors.

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  • Length converter
  • Weight converter
  • Volume converter
  • Temperature converter
  • Area converter
  • Speed converter
  • Cooking measurement converter
  • Pressure converter
  • Data storage converter
  • Fuel economy converter

Percentage calculators

5 tools. Percent of a number, percent change and difference, discounts and reverse percentages.

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Date and time calculators

7 tools. Days between dates, ages, date arithmetic, time zones, durations and week numbers.

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Everyday math

7 tools. Fractions, decimals, ratios, averages, rounding, GCF and LCM, Roman numerals.

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Practical calculators

7 tools. Tips, unit prices, fuel cost and mileage, electricity cost, recipes and pace.

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Six tools that answer the questions people ask most often in a kitchen, a shop or a calendar.

Cooking measurement converter

US, label, metric and Japanese cups, plus US, metric and Australian spoons, in milliliters.

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Percentage calculator

Find P% of X, what percent A is of B, or the whole when you know a part and its percent.

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Days between dates

Days, weeks, months and weekdays between two dates, counted with or without the end date.

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Temperature converter

Celsius, Fahrenheit, kelvin and Rankine, with the formula shown for every pair.

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Fraction calculator

Add, subtract, multiply and divide fractions and mixed numbers, simplified, with the working.

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Tip calculator

Tip amount, total and each person's share, with an option to tip on the subtotal and round shares up.

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Checked before you see it

Formulas live in small, tested code modules. The same code draws the tables on each page and runs the calculator.

Read the method
36calculators and converters
82units of measure, each with its defining factor
0bytes of your input sent anywhere
5topic collections

About these tools

Short answers about how the site works. Anything else: contact us.

Do you keep what I type?

No. Every calculation runs in your browser with JavaScript. The numbers, dates and lists you enter are not sent to our server or stored.

How precise are the results?

Converters use exact definitions and show up to ten significant digits. Fractions and rounding are done on exact digits, so 1.005 rounds to 1.01 as it would on paper. Round the result to the precision of your own measurement.

Which measuring systems do you cover?

Metric (SI), US customary and British imperial units side by side, plus country-specific kitchen measures such as metric, Japanese and Australian cups and spoons.

Can I use the results for medical, legal or engineering work?

The tools are for everyday reference. When a figure matters for health, law, safety or a contract, confirm it with the responsible professional or authority.