Unit Converter - Length, Mass, Volume, Temperature, Steps

Unit Converter Calculator

Updated Aug 10, 2026 By Jehan Wadia

Length Converter

FROM

Value to convert

Decimals, negatives and scientific notation (e.g. 1.5e3) are accepted.

From unit

Converted result

You can type here too — the “From” value converts in reverse.

To unit

Introduction

This Unit Converter Calculator changes one unit into another in seconds. Type a number, pick your two units, and see the answer right away. It works for length, weight, temperature, volume, area, speed, time, pressure, energy, power, angle, and frequency.

Need centimeters to inches? Kilograms to pounds? Celsius to Fahrenheit? Miles to kilometers? Liters to gallons? Just tap a category or use a quick link. You can also search for a unit by name, symbol, or nickname, like "lbs" or "kph".

The tool shows more than a number. It gives step-by-step math so you can see how the answer was found. It also lists your value in every unit of that group and draws a chart to compare them. You can set how many digits you want, swap the units with one click, and copy the result.

Use it for school work, cooking, travel, DIY projects, science class, or shipping. It is free, fast, and easy to use on a phone or computer. If you work mainly in metric units, the Metric Conversion Calculator covers those swaps in more depth.

How to use our Unit Converter Calculator

Pick a category, type a number, and choose your units. The tool shows the converted answer, the math steps, a table of every unit, and a bar chart.

Measurement Category: Click a tab like Length, Weight, Temperature, or Speed. This sets the list of units you can pick from.

Value to convert: Type the number you want to change. You can use decimals, negative numbers, and science notation like 1.5e3. For help writing very large or very small numbers, see the Scientific Notation Calculator.

From unit: Choose the unit your number is in now, such as meters, pounds, or Celsius.

To unit: Choose the unit you want the answer in, such as feet, kilograms, or Fahrenheit.

Converted result: Read your answer here. You can also type in this box, and the "From" value will convert backward.

Swap button: Click the arrows to flip the two units and convert the other way.

Result Precision: Pick how many digits you want in the answer. More digits give a more exact result. The Sig Fig Calculator and Rounding Calculator help if you need to match a set number of digits.

Find Units to Convert: Type a unit name, symbol, or nickname, like "kg" or "lbs". Pick one from the list and click Find Conversion. Only one box is needed.

Common Conversions: Click a quick link like "kg → lbs" or "Celsius → Fahrenheit" to set up that conversion in one step.

Buttons: Use Calculate to update the result, the X to clear both values, the copy icon to copy your answer, and Reset to start over.

What Is Unit Conversion?

Unit conversion means changing a measurement from one unit to another without changing the actual amount. A person who is 6 feet tall is also 1.83 meters tall. Both numbers say the same thing. Only the unit changed.

Every conversion works with a conversion factor. That is a number that links two units. For example, 1 inch equals 2.54 centimeters. So you multiply inches by 2.54 to get centimeters, or divide centimeters by 2.54 to get inches. The Ratio Calculator and Proportion Calculator are handy when you want to scale values by hand.

Measurement Systems

Most conversions move between two main systems:

Metric (SI): meters, grams, liters. Units grow and shrink by powers of 10, so math is easy. Used by most of the world.
Imperial / US customary: inches, feet, miles, pounds, gallons. Used mostly in the United States. The steps between units are not round numbers (12 inches in a foot, 5,280 feet in a mile). The Feet and Inches Calculator helps with mixed measurements.

Watch out for units that share a name but not a size. A US gallon (3.785 liters) is smaller than an imperial gallon (4.546 liters). A US ton (2,000 pounds) is lighter than an imperial long ton (2,240 pounds). Common swaps have their own pages too, like Pounds to Kilograms, Grams to Ounces, Ounces to Grams, MM to Inches, Inches to MM, Inches to CM, Meters to Feet, and Feet to Meters.

Common Conversion Factors

1 inch = 2.54 centimeters
1 foot = 0.3048 meters
1 mile = 1.609 kilometers
1 kilogram = 2.205 pounds
1 liter = 0.264 US gallons
1 acre = 4,047 square meters (see the Sq Ft to Acres Calculator)
1 kilowatt = 1.341 horsepower (see the Horsepower Calculator)

Why Temperature Is Different

Most units only need multiplying. Temperature also needs adding or subtracting, because the scales start at different points. Water freezes at 0 °C but at 32 °F. To go from Celsius to Fahrenheit you multiply by 9/5, then add 32. To go back, subtract 32, then multiply by 5/9, which the Fahrenheit to Celsius Calculator handles for you. Kelvin starts at absolute zero, the coldest possible point, so Kelvin equals Celsius plus 273.15. The general Temperature Calculator covers all four scales.

Squared and Cubed Units

Area and volume units follow the same rule, but the factor gets raised to a power. Since 1 foot is 0.3048 meters, 1 square foot is 0.3048 × 0.3048 = 0.0929 square meters. And 1 cubic foot is 0.3048 × 0.3048 × 0.3048 = 0.0283 cubic meters. This is why a small length change makes a big area or volume change. For dedicated tools, try the Area Converter Calculator, the Volume Conversion Calculator, the Cubic Feet Calculator, or the Cubic Yard Calculator.

Where Conversions Matter

Cooking uses cups, milliliters, and grams. Travel uses miles, kilometers, and Celsius, along with time zone math. Building and DIY work uses inches, millimeters, and square feet. School science uses meters, joules, and newtons, where the Force Calculator and Kinetic Energy Calculator come in handy. Shipping uses pounds and kilograms, so the Volumetric Weight Calculator and CBM Calculator pair well with this page. Getting the unit wrong can cost money or ruin a project, so it helps to double check the factor before you build, bake, or buy.

Tips for Accurate Results

You can only convert units that measure the same thing. Meters cannot become kilograms.
Round only at the end. Rounding early builds up error, which you can measure with the Percent Error Calculator.
Keep more digits for science and engineering work, fewer for everyday use.
Always write the unit next to the number so nobody has to guess.

Formulas used

Convert value to base unit (factor-based)

x_{\text{base}} = v \times f_{\text{from}}

Convert base value to target unit

v_{\text{to}} = \frac{x_{\text{base}}}{f_{\text{to}}}

Single-step conversion factor

v_{\text{to}} = v \times \frac{f_{\text{from}}}{f_{\text{to}}}

Temperature to kelvin (base scale)

T_K = T_C + 273.15 \qquad T_K = (T_F - 32)\times\frac{5}{9} + 273.15 \qquad T_K = T_R \times \frac{5}{9}

Kelvin to target temperature scale

T_C = T_K - 273.15 \qquad T_F = (T_K - 273.15)\times\frac{9}{5} + 32 \qquad T_R = T_K \times \frac{9}{5}

Logarithmic chart scale trigger (spread of values)

\frac{\max |v_i|}{\min |v_i|} > 1000

Frequently asked questions

Why can't I convert kilograms into meters?

Units must measure the same kind of thing. Kilograms measure mass and meters measure length, so there is no factor that links them.

If you pick units from two different categories in the search boxes, the tool will tell you they cannot be converted. Pick two units from the same category instead.

What does an answer like 1.5e-7 mean?

That is scientific notation. It is a short way to write very big or very small numbers.

1.5e-7 means 1.5 × 10^-7, or 0.00000015
3.2e6 means 3.2 × 10⁶, or 3,200,000

You can also type numbers this way in the value box.

What does the Result Precision setting really change?

It sets how many significant digits show in your answer, from 2 up to 17.

Pick 3 or 4 for cooking and everyday jobs. Pick 8 or more for science, engineering, or money-related math. The tool always does the math with full accuracy and only rounds the number you see.

Why doesn't converting back give me my exact starting number?

The number you see is rounded to your chosen precision. When you convert that rounded number back, the last digit can shift a little.

Raise the Result Precision to 12 or more and the round trip will match.

What do the colored rows in the unit table mean?

The purple row is your "From" unit. The green row is your "To" unit.

Every other row shows the same amount written in a different unit of that category, so you can compare all of them at once.

Why is the bar chart sometimes on a log scale?

Some categories have units of very different sizes, like millimeters and light years. On a normal chart, the small bars would vanish.

When the biggest value is more than 1,000 times the smallest, the tool switches to a log scale so every bar stays visible. The label under the chart says when this happens.

What is the "base unit" in the step-by-step math?

It is the main SI unit for that category, like the meter for length or the kilogram for mass.

The tool first turns your value into the base unit, then turns the base unit into your target unit. This keeps every conversion accurate and easy to follow.

Can I enter a fraction like 1/2?

No. The value boxes only take numbers. Type 0.5 instead of 1/2, 0.25 instead of 1/4, and 0.75 instead of 3/4.

How do I convert a height like 5 feet 10 inches?

Turn it into one unit first. There are 12 inches in a foot, so 5 ft 10 in is 70 inches.

Then pick Length, choose Inch as the From unit, type 70, and pick your To unit. You will get 177.8 centimeters or 1.778 meters.

Can I type a temperature below absolute zero?

The tool will still do the math, but the answer is not real. Nothing can be colder than 0 K, which is -273.15 °C or -459.67 °F.

If you see a negative Kelvin value in the steps, check your input.

Is the pound here a weight or a mass?

It is treated as mass, using the international pound of exactly 0.45359237 kilograms.

That is what scales, recipes, and shipping labels use, so the answers match everyday life.

Why do Month and Year say "average"?

Months have 28 to 31 days and some years have 366 days, so there is no single exact length.

The tool uses an average year of 365.25 days and an average month of about 30.44 days. Use it for rough planning, not for exact calendar dates.

What speed does Mach 1 use?

Mach 1 here is 340.29 meters per second, the speed of sound in dry air at sea level and 15 °C.

Sound moves slower in colder, thinner air, so real Mach speeds at high altitude are lower.

Why does my answer show 0?

The result is likely tiny, not truly zero. For example, 1 millimeter is 0.000000621 miles.

Raise the Result Precision to see more digits, or pick a smaller target unit.

How accurate are the conversion factors?

They use official exact definitions where they exist. For example, 1 inch is exactly 2.54 cm, 1 pound is exactly 0.45359237 kg, and 1 mile is exactly 1,609.344 m.

Factors that are not exact, like horsepower or BTU, use the standard accepted values.

Does the copy button copy the rounded number?

It copies exactly what is in the "Converted result" box, at your current precision setting.

Set the precision first if you need more digits, then click copy.

What is the difference between the tabs and the search box?

The tabs pick a whole category, like Length or Energy. The search box finds one unit by name, symbol, or nickname, such as "kph", "lbs", or "sq ft".

When you use search, the tool jumps to the right category and sets the units for you.

Can I convert data sizes, fuel economy, or currency here?

No. This tool covers 12 categories: length, temperature, area, volume, mass, time, speed, pressure, energy, power, angle, and frequency.

Data storage, fuel economy, and money need their own tools, since currency rates change every day.

Do I need to sign up or install anything?

No. The converter runs in your browser, is free, and saves nothing you type. It works on phones, tablets, and computers.