UNIT CONVERTER
All conversions run client-side using these constants. No API call, no rounding from the server, no precision loss in transit.
Updated May 2026 · Built by Lukáš, an architect in Prague.
Formula, assumptions, rounding & limitations
Formula
- Length:
value × factor (1 in = 0.0254 m) - Weight:
value × factor (1 lb = 0.45359237 kg) - Temperature C→F:
°F = °C × 9/5 + 32 - Temperature F→C:
°C = (°F − 32) × 5/9 - Temperature C↔K:
K = °C + 273.15
Assumptions
- Length and weight use exact international conversion factors.
- Temperature scales (Celsius, Fahrenheit, Kelvin) pivot through Celsius internally.
- Both decimal comma (1,5) and decimal point (1.5) are accepted.
Rounding
- Results are displayed with adaptive decimal precision: 2 places for values ≥ 100, 3 places for 1–99, 4 places for < 1.
Limitations
- Volume (liters, gallons), area (m², ft²), and speed (mph, km/h) are not included in this tool.
- US and UK Imperial gallons differ (3.785 L vs 4.546 L); volume conversion needs a dedicated tool.
- Surveying-specific units (US survey foot, nautical mile) and historic units are not included.
How do I convert kg to pounds in my head?
Multiply by 2.2 (close enough for casual use). 70 kg ≈ 154 lb. For exact, use 2.2046. Going the other way, divide pounds by 2.2 to get kg.
How do I convert Celsius to Fahrenheit quickly?
Double it and add 30 (rough). 20 °C → 40 + 30 = 70 °F (actual: 68 °F). For exact, use °F = °C × 9/5 + 32. The shortcut is wrong by 1–2 degrees but good enough for weather and cooking.
Why is 0 K not 0 °C?
Kelvin is an absolute scale starting at the coldest possible temperature (no molecular motion). 0 K = −273.15 °C. Celsius starts at the freezing point of water for convenience, not for physics.
What about volume, area, or speed?
Not in this tool. We kept the converter small on purpose — length, weight, and temperature cover the most common everyday cases. Volume (gallons, liters) and speed (mph, km/h) may be added later.