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unit-converter

A unit converter translates a quantity from one unit of measurement into another across multiple physical categories — length, weight, volume, area, temperature, time, energy, pressure, and speed — using exact conversion factors based on SI definitions. The ZTools Unit Converter handles 100+ common units across 12 categories, updates results live as you type, supports both metric and imperial systems plus regional variants (US gallons vs UK gallons), and shows the conversion formula so users learn the relationship rather than relying blindly on the result.

Use cases​

Cooking with international recipes​

A British recipe calls for "200 g flour and 150 ml milk". Convert to US cups for the kitchen. Avoids the "approximate it and hope" approach.

Travel and shopping abroad​

Hotel says room is "32 m²" — that's 344 sq ft. A 5 km run is 3.1 miles. Quick conversions while on the road.

Engineering and science homework​

Convert 4.5 kJ to calories, 60 mph to m/s, 1 atm to kPa. The converter handles the unit math; you focus on the physics.

Construction and DIY measurements​

Lumber sold in feet, plans in metric. Convert quickly without misreading the tape and cutting an inch short.

How it works​

  1. Pick a category — Length, weight/mass, volume, area, temperature, time, energy, pressure, speed, data storage, fuel economy, angle.
  2. Enter the source value and unit — Decimals accepted. Negative values OK for temperature and signed quantities.
  3. Pick the target unit — All compatible units in the same category appear as options. Live conversion as you type or select.
  4. Read the result and the formula — Final value plus the conversion factor used (e.g., 1 mile = 1.609344 km). Copy the result with one click.
  5. Optionally view all conversions at once — A "convert to all" mode shows the source value in every unit in the category — handy when you're unsure which unit you actually need.

Examples​

Input: 5 miles to km

Output: 8.04672 km (1 mile = 1.609344 km)

Input: 70 °F to °C

Output: 21.111 °C ((70 − 32) × 5/9)

Input: 1 cubic foot to liters

Output: 28.3168 L

Frequently asked questions​

Why are US and UK gallons different?

1 US gallon = 3.785 L; 1 UK (imperial) gallon = 4.546 L. Different historical definitions. Always check which "gallon" a recipe or spec means — about 20% difference.

Is the conversion exact?

For most units, yes — modern SI definitions are exact. Inch is exactly 25.4 mm. Pound is exactly 0.45359237 kg. Some derived units (BTU, calorie) have multiple definitions; the converter notes which it uses.

How do I convert temperature?

Temperature isn't a simple multiplication — it has an offset. °F to °C: (F − 32) × 5/9. °C to K: C + 273.15. The converter handles all the offsets correctly; don't try mental math for temperature.

Can it convert currency?

No — currency conversion needs live exchange rates. Use the dedicated Currency Converter for that. This tool covers physical units only.

What's the difference between mass and weight?

Mass is the amount of matter (kg, lb-mass). Weight is force (N, lb-force) and depends on gravity. Outside physics class, "pounds" and "kilograms" are usually used as mass; the converter follows that convention.

Tips​

  • For very large or very small values, use scientific notation (1e6 = 1,000,000) — the converter handles it.
  • Keep a few common conversions memorized: 1 mile ≈ 1.6 km, 1 inch = 2.54 cm, 1 kg ≈ 2.2 lb, 0 °C = 32 °F.
  • For cooking, weight is more accurate than volume — 200 g of flour is consistent; 1 cup varies with packing.
  • When precision matters (engineering, medicine), always work in SI units and convert at the end.

Try it now​

The full unit-converter runs in your browser at https://ztools.zaions.com/unit-converter — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-05 · Author: Ahsan Mahmood · Edit this page on GitHub