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Convert any unit, instantly

12 categories · 100+ units · 1,135 conversion pairs. Pick a popular conversion below or use the live calculator.

metre
foot
1 m = 3.2808ft
Try: 1 kg → lb · 0 °C → °F · 1 GB → MB · 30 MPG → L/100km

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Length 13 units Temperature 5 scales Data 12 prefixes PNG compressor no upload

How it works

  1. 1

    Pick two units

    Choose any unit pair from the same category — metres↔feet, °C↔°F, GB↔MB, and so on.

  2. 2

    Type a number

    Type any value on either side. The other side updates instantly — no submit button.

  3. 3

    Read the result

    Get the exact value plus a 10-row reference table, FAQs, and related conversions.

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Universal calculator

Pick any two units from the same category. Type on either side, the other updates live.

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Browse by category

Every unit on this site belongs to one of these categories. Each unit page explains where it comes from, gives a conversion table, and links to popular pair pages.

Length
13 units · base: m
Distance, height, width — anything that measures how long something is. SI base unit: the metre (m).
Mass
10 units · base: kg
How much matter is in something. Differs from weight (which is force). SI base: kilogram (kg).
Temperature
5 units · base: K
How hot or cold something is. Conversions are affine — there is an offset, not just a multiplier.
Area
9 units · base: m²
Size of a 2-D surface. SI base: square metre (m²).
Volume
14 units · base: L
Space occupied by a 3-D object. SI base: litre (L) for everyday use; cubic metre (m³) for SI.
Speed
6 units · base: m/s
Distance per unit time. SI: metre per second (m/s).
Time
12 units · base: s
Duration. SI base: the second (s).
Data
12 units · base: B
Digital information size. SI: the byte (B). Note the difference between decimal (KB=1000) and binary (KiB=1024) prefixes.
Energy
10 units · base: J
Capacity to do work. SI base: joule (J). Also commonly expressed as calories, kWh, BTU.
Pressure
8 units · base: Pa
Force per unit area. SI base: pascal (Pa).
Angle
6 units · base: rad
Rotation or turning. SI base: radian (rad).
Fuel Economy
4 units · base: L/100km
Distance per unit of fuel, or its reciprocal (fuel per distance). Base: litres per 100 km.

Popular conversions

The most-searched unit pairs. Click for a full conversion table, the math, and an FAQ.

meter → foot foot → meter kilometer → mile mile → kilometer inch → centimeter centimeter → inch mile → foot yard → meter kilogram → pound pound → kilogram gram → ounce ounce → gram celsius → fahrenheit fahrenheit → celsius celsius → kelvin liter → gallon gallon → to liter → milliliter square → to square → to hectare → acre acre → hectare kilometer → hour mile → hour knot → mile knot → kilometer mach → kilometer hour → minute minute → second day → hour week → day year → day byte → kilobyte kilobyte → byte kilobyte → kibibyte kibibyte → kilobyte gigabyte → megabyte terabyte → gigabyte megabyte → mebibyte gigabyte → gibibyte

Browse all conversion pairs

Articles & explainers

Reference

What is a unit? A practical guide

Why every measurement needs a unit, the difference between base and derived units, and why SI exists.

6 min Data

Why KB and KiB are different — and why it matters

Disk drives advertise GB, but your OS reports GiB. This article explains the 1000-vs-1024 divide.

5 min Length

Metric vs Imperial: which countries still use imperial?

A quick map of who uses which — and where metric beats imperial at scale.

4 min Temperature

Celsius to Fahrenheit explained — the formula and the intuition

F = C × 9/5 + 32. Here is why that formula is what it is.

4 min

Read all articles

FAQ

What is unitbox?

unitbox is a network of unit-conversion pages: every popular unit gets a detail page, and every popular pair gets a converter. Length, mass, temperature, area, volume, speed, time, data, energy, pressure, angle, and fuel-economy.

How accurate are the conversions?

All conversions use the standard SI conversion factors. For mass, length, time, the values match NIST to the precision shown. Temperature uses the affine offset/scale formulas; the precision is 2 decimal places by default.

What is the difference between KB and KiB?

KB (kilobyte) = 1000 bytes — the SI decimal prefix. KiB (kibibyte) = 1024 bytes — the binary prefix designed to remove ambiguity. Disk drives advertise KB; RAM and operating systems often show KiB. For more, see the learn page on data units.

How do you handle fuel economy?

We treat fuel-economy as a reciprocal quantity. The base unit is L/100 km (lower is better); MPG-US, MPG-UK, and km/L are stored as reciprocals. Converting 30 MPG-US gives 7.84 L/100km.

Does this work offline?

Yes — every page is statically generated. Once loaded, the converter widget runs without a network roundtrip. Bookmark any pair page.

Can AI agents cite unitbox?

Yes — point your agent at https://unitbox.online/llms.txt and /openapi.json. The site is built to be AI-friendly by default: JSON-LD, schema.org, and a machine-readable product brief.

People also ask

metres to feet celsius to fahrenheit kg to lbs miles to km litres to gallons inches to cm GB to MB hours to minutes psi to bar joules to calories hectares to acres kelvin to celsius knots to mph degrees to radians mpg to l/100km
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unitbox API · Convert any unit from any AI agent

Open conversion engine for Claude, Cursor, Codex, and any HTTP-compatible AI agent. Free, MIT-licensed, no rate limit.

$ curl 'https://api.unitbox.online/v1/convert?from=meter&to=foot&value=1'
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