ZapUnits — the easy way to convert units
Type a number, pick two units, read the answer. Then see the whole relationship on a graph, and keep a history of every conversion you have run.
Kilometers
42.195
Miles
26.219
- km
- °C
- GB
- psi
- acre
- lb
- mmHg
- kWh
- mi
- ha
- m/s
- °F
- ft
- gal
- bar
- N·m
…and 616 more, across 64 categories
Quick convert
All converters
Pick a category to convert between any two of its units.
Most searched conversions
Straight to the answer — each page includes the formula and a chart.
Every conversion, one keystroke away
632+ units across 64 categories — from centimetres and kilowatt-hours to bighas, centipoise and blood glucose. Search finds the unit before you finish typing it.
See the relationship, not just the number
Every conversion plots on an X/Y graph so you can read off any value at a glance — and see immediately why fuel economy and pace curve instead of running straight.
Your history, saved and chartable
Create a free account and every conversion you run is kept. Pull the list back up later, filter it, and plot your past conversions on the same chart.
Your conversions, kept and charted
Sign in and every conversion you run is saved automatically — no button to remember. Come back later, filter by category, and pick any entry to see it plotted.
Run the same conversion more than once and it becomes a series: input and result tracked over time, so you can watch a figure move across a project rather than recalculating it from scratch.
From the blog
Guides that explain the units, not just the arithmetic.
Lunar Time: Why Clocks Run Faster on the Moon
The United States has told NASA to build a lunar time standard by the end of 2026. The reason is not tidiness: a clock on the Moon genuinely ticks faster than one on Earth, by about 56 microseconds every day.
GSM Explained: Fabric and Paper Weight Without the Guesswork
One ounce per square yard is 33.906 GSM, exactly. US paper weights are harder, because every grade is weighed at a different sheet size.
Isometric Graph Paper: How to Draw in 3D Without Perspective
Three line families, sixty degrees apart, and no vanishing point. Isometric paper lets you draw something in 3D and still measure it.