Unit Converter
Convert data, time, length, mass, temperature, and more with precision.
Unit Converter
Convert data, time, length, mass, temperature, and more with precision.
Features
- Multiple conversion categories: length, weight, temperature, volume, area, time, data (SI + IEC bytes), and energy — each backed by a unit engine that handles non-linear conversions (e.g. °C↔°F) correctly
- Precision dial 0–12 with five rounding modes (half-up, banker's, floor, ceiling, truncate) so the output matches what your downstream system expects
- IEC/SI distinction for data units exposed explicitly: 1 KB = 1000 B vs 1 KiB = 1024 B — the conversion picks the right ratio based on which suffix you select
- Multi-target panel: enter a single value once and see it expressed in every other unit of the same category, useful for translating between metric and imperial in one glance
- Mixed-unit expression input: type "5ft 7in" or "5' 7\"" and the parser converts both parts to the base unit
- Permalink sharing — the URL captures category, units, value, precision, and rounding; pasting into another browser restores the exact same conversion
- Favourite unit pairs + recent conversions persist in localStorage so the pairs you use daily stay one click away
- Pure client-side: the unit registry ships in the JS bundle, no API calls; the page works offline once cached and DevTools Network stays empty during conversions
How to use
- Pick a category tab (Data, Time, Length, etc.) — the from/to dropdowns update to that category's units.
- Enter a value in the from-field; the conversion runs as you type with the chosen precision.
- Select target units in the to-field, or use the multi-target panel to see every unit at once.
- Adjust precision (0–12) and rounding mode (half-up, banker's, floor, ceiling, truncate) if the default doesn't match what you need.
- Click Swap to reverse the direction, Copy to grab the result, or Share to copy a permalink that reproduces the exact state.
- Star a pair (e.g. KB → MB) to keep it in Favourites for the same category next time.
Tips & Best Practices
- For scientific work, use 10–12 digits of precision and banker's rounding when you plan to sum many converted values.
- When converting storage sizes, double-check whether the source uses SI (1000) or IEC (1024) — picking the wrong suffix changes results by 2–10% at large sizes.
- Use the permalink share when documenting a specific conversion in a README or chat — it survives library updates and proves the exact precision you used.
- Mixed-unit input like `5ft 7in` is faster than two separate fields when you have height in imperial; verify the parsed total in the result row before copying.
- Favourites are per-category — star KB→MB once and it stays in Data; star kg→lb separately for Weight.
FAQ
What's the difference between KB and KiB?
KB is decimal (1000 bytes); KiB is binary (1024 bytes). Storage manufacturers use KB/MB/GB/TB; operating systems and memory specs use KiB/MiB/GiB/TiB. A "500 GB" disk has ~465 GiB of binary capacity — same number of bytes, two ways of naming the same quantity.
Why do my temperature conversions show decimals?
Celsius, Fahrenheit, and Kelvin scales use different zero points and step sizes. Converting 100°F to °C gives 37.7777…°C exactly; the precision dial controls how many of those decimals you see. Round numbers in one scale are almost never round in another — that's the math, not a tool quirk.
How precise are time conversions?
Second-scale conversions (ms ↔ s ↔ min ↔ h ↔ day) are exact within the precision you select. Month and year use fixed approximations (30.44 days/month, 365.25 days/year) since they vary across the calendar; for date-aware deltas use the Date Calculator instead.
How do I enter mixed units like feet and inches?
Type expressions like `5ft 7in` or `5' 7"` in the from-field; the parser combines both parts and converts them to the base unit (meters in this case). Works for length and weight; temperature/volume don't mix the same way.
Which rounding mode should I use?
Half Up is the default and matches school-arithmetic rounding (0.5 rounds up). Banker's (half-to-even) minimises bias when you sum many rounded values — useful for financial workflows. Floor/Ceiling/Truncate let you force a direction when the consumer needs predictable behaviour at boundaries.
Can I add my own custom units?
Not from the UI — the unit registry ships in the bundle. If you have a unit that belongs in the standard set (a niche scientific unit, a regional unit), open a GitHub issue with the symbol, name, and conversion factor to the base unit.
Does the conversion happen on a server?
No. The full unit registry ships in the JS bundle, the math runs in your tab, and the result renders synchronously. DevTools Network stays empty during conversions; the page works offline once cached.
How does the permalink share work?
Click Share to copy a URL that encodes the category, both units, the value, precision, and rounding mode. Open the URL in any browser (or send it to a colleague) and the page restores the exact same conversion immediately — useful for embedding specific conversions in docs or chat.