Toolivaro

Free Unit Converter

Convert length, weight, temperature, volume, and speed between metric and imperial units with exact conversion factors.

Processed locally in your browser

About this tool

The unit converter handles the five most common conversion families — length, weight, temperature, volume, and speed — between metric and imperial units. Pick a category, choose the from-unit and to-unit, and enter a value: inches to centimeters, pounds to kilograms, Fahrenheit to Celsius, US gallons to liters, miles per hour to kilometers per hour, and more than two dozen other pairs. Every linear conversion uses the exact defining factors (for example 1 inch ≡ 2.54 cm and 1 pound ≡ 0.45359237 kg, per the SI brochure), so a mile converts to exactly 1.609344 kilometers — not an approximate value. Temperature is converted with the affine formulas, including the Kelvin scale, and the tool correctly handles the −40° crossover where Celsius and Fahrenheit are equal. All conversions run locally in your browser with decimal precision; nothing you enter is sent to a server.

How is the result calculated?

A 27-inch screen in centimeters

With length selected and from-inch to-centimeter, entering 27 gives 27 × 2.54 = 68.58 cm — the exact diagonal of a standard desktop monitor.

Input Value
category length
from inch
to centimeter
value 27
Result 68.58 cm

Normal body temperature in Celsius

With temperature selected and from-Fahrenheit to-Celsius, entering 98.6 gives (98.6 − 32) × 5/9 = 37.0 °C.

Input Value
category temperature
from fahrenheit
to celsius
value 98.6
Result 37 °C

What is the formula and its assumptions?

Linear unit conversion

valueInToUnit = value × factorFrom / factorTo

Symbol Meaning
factorFrom the from-unit's factor to the base unit
factorTo the to-unit's factor to the base unit

Celsius to Fahrenheit

°F = °C × 9/5 + 32

Symbol Meaning
°C temperature in degrees Celsius
°F temperature in degrees Fahrenheit

Fahrenheit to Celsius

°C = (°F − 32) × 5/9

Symbol Meaning
°F temperature in degrees Fahrenheit
°C temperature in degrees Celsius

What are the most common mistakes?

  • Confusing US and UK gallons — a US gallon is about 20% smaller than a UK gallon.
  • Treating Fahrenheit and Celsius as proportional — they share an offset, so "doubling" a temperature in one scale does not double it in the other.
  • Mixing weight and volume units (pounds with gallons) for liquids — those need density, which this converter does not assume.

What are the assumptions and limitations?

  • Weight-to-volume conversions (e.g. pounds of water to gallons) are not supported because they depend on density.
  • The converter covers everyday units; specialized fields such as energy, pressure, or data storage are not included.
  • Results are exact conversions, not engineering tolerances — for legal or regulated use, consult the relevant standards.

Where do the numbers come from?

Last reviewed August 11, 2026 · Version 1.0.0 · Toolivaro does not guarantee external content.

Math Percentage Calculator Four percentage calculations in one tool: X% of Y, X is what % of Y, % change from X to Y, and Y plus or minus X%. Time Date Difference Calculator Calculate the exact number of days, weeks, months, and years between two dates — with a single trusted method. Time Time Zone Converter Convert any date and time between IANA time zones with correct daylight-saving handling and explicit offsets. Health BMI Calculator Calculate your Body Mass Index from metric or imperial measurements, with the WHO classification and a healthy weight range.

Frequently asked questions

Are the conversion factors exact?

Yes. Length, weight, and volume use the exact defining factors from the SI brochure — an inch is defined as exactly 2.54 cm and a pound as exactly 0.45359237 kg. The displayed result is rounded, but the conversion itself never loses precision.

What is the difference between a US gallon and a UK gallon?

A US gallon is exactly 3.785411784 liters while a UK (imperial) gallon is exactly 4.54609 liters — about 20% larger. The converter treats them as separate units because confusing the two is a classic source of recipe and fuel-economy errors.

Why is −40 the same in Celsius and Fahrenheit?

The two scales cross at −40: −40 × 9/5 + 32 = −40. It is the only temperature where both readings are equal, and the converter handles it exactly.

Part of Format and conversion tools

Found a mistake or have a correction? Report it — we review every correction.

Was this helpful?

Reviewed by the Toolivaro editorial team per our methodology Methodology · Editorial policy