Unit Conversion Calculator

What Is a Unit Conversion Calculator?

A unit conversion calculator translates a measurement from one unit to another — miles to kilometers, pounds to kilograms, gallons to liters, Fahrenheit to Celsius. Anyone who travels, cooks from foreign recipes, shops internationally, or works in science and engineering runs into mismatched units constantly. The calculator applies exact conversion factors so you get precise answers without memorizing constants.

How Conversion Math Works

Most conversions are simple multiplication by a defined factor:

value in new unit = value in old unit × conversion factor

For example, the mile is defined as exactly 1,609.344 meters, so 1 mile = 1.60934 km. Converting back just divides by the same factor (or multiplies by its reciprocal). Temperature is the exception — it needs an offset as well as a scale:

• °F to °C: (°F − 32) × 5/9
• °C to °F: (°C × 9/5) + 32
• °C to K: °C + 273.15

A good converter chains these automatically: converting miles per hour to meters per second, for instance, combines the length and time factors in one step.

How to Use This Calculator

1. Pick the category (length, weight, volume, temperature, speed, etc.).
2. Enter the value, choose the from unit and the to unit.
3. Read the result — many converters also show the conversion factor used, so you can sanity-check it.

Worked Example

Example 1 — length: convert 5 miles to kilometers. The factor is 1.60934 km per mile: 5 × 1.60934 = 8.0467 km.

Example 2 — temperature: convert 100°F to Celsius: (100 − 32) × 5/9 = 68 × 5/9 = 37.78°C — just below normal body temperature, a useful sanity check that the formula is right.

Example 3 — weight: convert 70 kg to pounds: 70 × 2.20462 = 154.32 lb.

Tips

• US vs. imperial gallons: a US gallon is 3.78541 liters but an imperial (UK) gallon is 4.54609 liters — a 20% difference. Always check which gallon a recipe or spec means.
• Significant figures: don't report 8.04670 km when your input was "about 5 miles" — match your precision to your measurement.
• Troy vs. avoirdupois ounces: gold is weighed in troy ounces (31.1035 g), everything else in avoirdupois ounces (28.3495 g). Mixing them up overstates gold weight by nearly 10%.
• Temperature intervals: a change of 1°C equals a change of 1.8°F — the +32 offset only applies when converting absolute temperatures, not differences.