Unit Converter

How this converter works

Each category except temperature converts through a single base unit. Every unit is stored as a factor — how many base units it equals — so a conversion is just two operations: multiply your value by the source factor to get base units, then divide by the target factor. Length uses the metre as its base, mass the gram, volume the litre, area the square metre, speed metres per second, and data the byte. Because the factors are the exact internationally-agreed definitions (one inch is exactly 0.0254 m; one pound is exactly 453.59237 g), the results are accurate to the eight significant figures shown.

Ratio units vs offset units

Almost every unit here sits on a ratio scale: zero means "none of the quantity", and doubling the number doubles the amount, so one multiplication does the whole job. Temperature is the exception. Celsius and Fahrenheit are interval scales whose zero points were chosen arbitrarily, so converting between them needs both a ratio and an offset. That single distinction explains why every conversion below is one line of arithmetic except temperature, which needs two.

Worked example: km/h to m/s

Speed is a ratio unit, so the conversion is a plain multiply — or in this case a divide. One km/h is 1000 metres spread over 3600 seconds, which is 1000 ÷ 3600 = 0.27778 m/s, so to turn km/h into m/s you divide by 3.6. A car at 100 km/h ÷ 3.6 ≈ 27.78 m/s; a brisk 5 km/h walk is about 1.39 m/s. Reverse it by multiplying: a 10 m/s gust is 36 km/h. The factor 3.6 is exact because the kilometre and the hour are themselves exact multiples of the metre and the second.

Worked example: a temperature edge case

The formula is °F = °C × 9/5 + 32, so a warm 25 °C day is 25 × 9/5 + 32 = 77 °F, and the two scales cross at −40°, where −40 °C = −40 °F. The edge case that trips people up is a temperature difference: because the offset is baked into each reading, it cancels when you subtract two of them. A rise of 10 °C is a rise of 10 × 9/5 = 18 °F, not 50 °F. Use the full formula for a specific temperature, but only the 9/5 ratio for an interval — a distinction that matters in cooking, HVAC and lab work alike.

Common conversion factors

Pressure, energy, power and angle

Four more ratio categories share the same base-unit machinery. Pressure works from the pascal: 1 bar is exactly 100,000 Pa and 1 atm is exactly 101,325 Pa (both defined values), while 1 psi is 6894.76 Pa — derived from the pound-force (0.45359237 kg × 9.80665 m/s²) spread over one square inch (0.00064516 m²). Energy works from the joule: 1 kWh is exactly 3.6 MJ (a kilowatt sustained for 3600 seconds), and the calorie here is the thermochemical one, defined as exactly 4.184 J — food labels use the kilocalorie, so a "200 calorie" snack is really 200 kcal ≈ 837 kJ. Power works from the watt, with mechanical horsepower fixed at 550 ft·lbf/s = 745.69987 W (note: metric and electrical horsepower differ slightly, so this tool uses the mechanical definition). Angle works from the radian: a full turn is 2π rad = 360° = 400 gon, so a degree is π/180 rad and an arcsecond is 1/3600 of a degree.

Fuel economy: the one category that is an inverse, not a ratio

Miles per gallon and litres per 100 km measure the same thing from opposite ends: mpg counts distance per unit of fuel, L/100km counts fuel per unit of distance. That makes them inverses — doubling one halves the other — so no fixed multiplier can link them the way 2.54 links inches and centimetres. The tool converts through km/L as a pivot and crosses the inverse boundary with L/100km = 100 ÷ (km/L). From the exact definitions (1 mile = 1.609344 km, 1 US gallon = 3.785411784 L) that works out to L/100km = 235.214583 ÷ mpg (US): a 23.5 mpg pickup burns about 10 L/100km, a 47 mpg hybrid about 5. Watch the gallon trap: an imperial gallon is 4.54609 L, about 20% bigger than the US one, so a UK "40 mpg" is only about 33.3 mpg US — same car, different gallon. The inverse also skews intuition: improving 15 → 20 mpg saves more fuel over a fixed distance than the much bigger-sounding jump from 40 → 60 mpg, which the L/100km view makes obvious — 15.7 → 11.8 L/100km saves 3.9 L every 100 km, while 5.9 → 3.9 saves only 2.0 L (check any of these in the tool). One honest edge: 0 mpg or 0 L/100km has no equivalent on the other scale (there is no inverse of zero), so the tool refuses it with a message instead of showing Infinity.

Kilobytes vs kibibytes, made explicit

The data category keeps the two byte families deliberately separate because they are genuinely different quantities. Decimal (SI) units step by 1000: 1 kB = 1000 B, 1 MB = 1000² = 1,000,000 B, and so on — this is what storage and network vendors advertise. Binary (IEC 80000-13) units step by 1024: 1 KiB = 1024 B, 1 MiB = 1024² = 1,048,576 B — this is what most operating systems count when they show a file or disk size. The gap compounds: it is 2.4% at the kilo step but about 10% by the tera step, which is why a "1 TB" drive shows as roughly 931 GiB. Every unit in the dropdown is labelled with its family and exact byte count so you always know which one you are converting.

Data-transfer rate: bits, bytes, and the decimal/binary split

The data rate category converts speeds, and it hides the single most common networking mistake: 1 byte = 8 bit, always. Internet plans and link speeds are quoted in bits per second (a "100 Mbit/s" line), while file copies and downloads are usually shown in bytes per second (your browser's "12 MB/s"). Because a byte is exactly eight bits, every byte-rate is exactly 8× the matching bit-rate, so a full 100 Mbit/s link tops out at only 100 ÷ 8 = 12.5 MB/s — not 100. That factor of eight, not any loss or overhead, is why a "1 Gbit/s" connection downloads at about 125 MB/s.

The same decimal-versus-binary split as for storage applies here, and this tool keeps the families distinct rather than fudging them together. Decimal (SI) prefixes step by 1000: 1 kbit/s = 1000 bit/s, 1 Mbit/s = 1,000,000 bit/s. Binary (IEC) prefixes step by 1024: 1 kibit/s = 1024 bit/s, 1 Mibit/s = 1,048,576 bit/s — so 1 Mibit/s and 1 Mbit/s are genuinely different rates (1,048,576 vs 1,000,000 bit/s), never interchangeable. Networking hardware almost always means the decimal forms, but the binary ones are here so nothing is guessed for you. Every factor in this category is a plain power of ten, a power of two, or that exact 8-bit byte relation — no rounded constants.

Frequency: Hz to GHz

The frequency category is the simplest kind: pure decimal SI, powers of ten with no binary variant to trip over. One hertz is one cycle per second, so 1 kHz = 1000 Hz, 1 MHz = 1,000,000 Hz, and 1 GHz = 1000 MHz = 1,000,000,000 Hz. A 2.4 GHz Wi-Fi channel is 2,400 MHz; the 44.1 kHz sample rate of a CD is 44,100 cycles per second. Unlike bytes, frequency prefixes are never binary — a "3 GHz" CPU clock is exactly three billion cycles per second.

Common mistakes

Mixing US and imperial. A US gallon is 3.785 L but a UK (imperial) gallon is 4.546 L, and a US pint is 473 mL against a UK pint's 568 mL — always know which system a recipe or spec means. Treating temperature like a ratio. Forgetting the +32 offset, or wrongly applying it to a difference, are the two classic slips covered above. Confusing mass with volume. "One millilitre equals one gram" holds only for water near 4 °C; for oil, flour or milk it is off by 5–20%, and this tool won't cross between the two on purpose. Ignoring decimal vs binary bytes. A "500 GB" drive is about 465 GiB once your operating system counts in powers of 1024 — the file didn't shrink, the units differ. Over-trusting the 2.2 shortcut. 1 kg is 2.20462 lb, so the rounded 2.2 drifts about 0.2%.

Honest limits

This tool converts between units of the same physical quantity only. It will not turn litres into kilograms — that needs the density of the specific substance. Fuel economy, the one inverse relationship here, gets its own dedicated category with proper 100÷x math rather than being shoehorned into a linear factor, and it refuses a zero input because zero has no inverse. US customary volumes are used for cup, pint and gallon (the fuel category is the exception that offers both gallons), so adjust if you need imperial elsewhere. Results are rounded for display to eight significant figures, which is far tighter than any everyday measurement, so the limiting factor is almost always how precisely you measured the input, not the conversion itself.