This unit converter handles 20 quantities and 200+ units, from everyday length and weight to the engineering units that general converters skip: kgf/cm² to MPa, lbf·ft to N·m, TR to kW, cfm to m³/h, centipoise, centistokes and MLD. Type a value and the answer updates as you type, with the exact conversion factor shown so you can reuse it in a hand calculation.
Unit Converter
Open Show this value in every unit under the result to see one value converted into every unit of that quantity at once, which is handy when a data sheet mixes bar, psi and kgf/cm². For metric prefixes (milli, micro, mega, giga) and metric-to-imperial charts, use our metric conversion chart and prefix converter.
What the converter covers
| Quantity | SI unit | Units included |
|---|---|---|
| Length | metre (m) | km, cm, mm, micron, nm, inch, foot, yard (gaj), mile, nautical mile, thou, angstrom |
| Area | m² | hectare, are, acre, ft², in², sq. yard, sq. mile, guntha, cent |
| Volume | m³ | litre, mL, cc, ft³, in³, US and UK gallon, quart, cup, fl oz, tbsp, tsp, oil barrel |
| Mass | kilogram (kg) | g, mg, tonne, quintal, pound, ounce, stone, short ton, long ton, tola, carat, grain |
| Temperature | kelvin (K) | °C, °F, K, °R |
| Pressure / stress | pascal (Pa) | kPa, MPa (N/mm²), GPa, bar, mbar, atm, psi, ksi, kgf/cm², mmHg, torr, inHg, mm and m of water |
| Force | newton (N) | kN, kgf, tonne-force, lbf, kip, dyne |
| Torque | N·m | kN·m, N·mm, kgf·m, kgf·cm, lbf·ft, lbf·in, ozf·in |
| Energy | joule (J) | kJ, MJ, Wh, kWh (the electricity “unit”), cal, kcal, food Calorie, BTU, ft·lbf, eV, erg |
| Power | watt (W) | kW, MW, hp, metric hp (PS), BTU/h, ton of refrigeration (TR), kcal/h |
| Flow rate | m³/s | m³/h, L/s, L/min, L/h, MLD, US and UK gpm, cfm, cusec |
| Others | speed, density, dynamic and kinematic viscosity, angle, time, data size (kB vs KiB), fuel economy (km/L, L/100 km, mpg) |
How unit conversion works
Unit conversion multiplies a value by a conversion factor: a fraction equal to 1 because its top and bottom are the same quantity in different units. Multiplying by 1 changes the units without changing the physical amount. For example, 1 in = 25.4 mm, so (25.4 mm / 1 in) = 1.
The factor-label method (dimensional analysis)
Write the value with its units, multiply by factors arranged so that unwanted units cancel top and bottom, and stop when only the target units remain.
Example 1: 72 km/h to m/s
72 km/h × (1000 m / 1 km) × (1 h / 3600 s) = 72 × 1000 / 3600 = 20 m/s. The km cancels with km and h with h. The shortcut “divide km/h by 3.6” is just this chain pre-multiplied.
Example 2: a 150 psi air receiver in bar and kgf/cm²
1 psi = 6894.757 Pa. So 150 psi = 150 × 6894.757 = 1,034,214 Pa. Divide by 100,000 Pa per bar: 10.34 bar. Divide the pascals by 98,066.5 Pa per kgf/cm²: 10.55 kgf/cm². Notice that bar and kgf/cm² are close but not equal (about 2% apart), a gap that matters when you check a gauge against a design pressure.
Example 3: bolt torque from an American manual
A manual specifies 40 lbf·ft. With 1 lbf·ft = 1.35582 N·m, 40 × 1.35582 = 54.2 N·m. Set a metric torque wrench to 54 N·m.
Squared and cubed units: the most common student error
When a unit is squared or cubed, the factor is squared or cubed too. 1 m = 100 cm, so 1 m² = 100² = 10,000 cm² (not 100), and 1 m³ = 100³ = 1,000,000 cm³ = 1000 litres. Likewise, a stress of 1 N/mm² is 1 N / (10−3 m)² = 106 Pa = 1 MPa. This is why structural engineers can use N/mm² and MPa interchangeably.
Temperature is the exception
Celsius and Fahrenheit have different zero points, so they need an offset as well as a factor: °F = °C × 9/5 + 32, and K = °C + 273.15. Body temperature 37 °C is 37 × 1.8 + 32 = 98.6 °F. The two scales cross at −40, where −40 °C = −40 °F. A temperature difference is different again: a rise of 10 °C is a rise of 18 °F (no +32) and exactly 10 K, which is why thermal expansion and heat-transfer formulas accept ΔT in either °C or K.
Exact conversion factors worth memorising
Many factors are exact by definition, not measured, so they carry no rounding error. Use these in hand calculations and quote them with confidence.
| Relationship | Value | Status |
|---|---|---|
| 1 inch | 25.4 mm | Exact (international agreement, 1959) |
| 1 foot | 0.3048 m | Exact |
| 1 mile | 1609.344 m | Exact |
| 1 pound (lb) | 0.45359237 kg | Exact (1959) |
| Standard gravity gn | 9.80665 m/s² | Exact, so 1 kgf = 9.80665 N |
| 1 standard atmosphere | 101,325 Pa | Exact |
| 1 bar | 100,000 Pa | Exact |
| 1 US gallon | 231 in³ = 3.785411784 L | Exact |
| 1 UK gallon | 4.54609 L | Exact |
| 1 calorie (thermochemical) | 4.184 J | Exact |
| 1 calorie (International Table) | 4.1868 J | Exact |
| 1 metric horsepower (PS) | 75 kgf·m/s = 735.49875 W | Exact |
| 1 horsepower (hp) | 550 ft·lbf/s ≈ 745.700 W | Derived from exact values |
| 1 ton of refrigeration (TR) | 12,000 BTU/h ≈ 3.517 kW | Derived |
| 1 kWh | 3.6 MJ | Exact |
Engineering conversion tables
Pressure and stress
| From | Pa | bar | psi | kgf/cm² |
|---|---|---|---|---|
| 1 MPa (N/mm²) | 1,000,000 | 10 | 145.04 | 10.197 |
| 1 bar | 100,000 | 1 | 14.504 | 1.0197 |
| 1 psi | 6894.76 | 0.068948 | 1 | 0.070307 |
| 1 kgf/cm² | 98,066.5 | 0.980665 | 14.223 | 1 |
| 1 atm | 101,325 | 1.01325 | 14.696 | 1.0332 |
Power, energy and cooling
| Conversion | Value | Where you meet it |
|---|---|---|
| 1 hp to kW | 0.7457 kW | Pump and motor name plates (US) |
| 1 PS (metric hp) to kW | 0.7355 kW | Indian and European car brochures |
| 1 TR to kW | 3.517 kW of cooling | AC and chiller capacity |
| 1 kWh to MJ | 3.6 MJ | Electricity bills (“units”) |
| 1 kcal (IT) to kJ | 4.1868 kJ | Older heat-transfer and boiler data |
| 1 BTU to kJ | 1.0551 kJ | HVAC and gas appliance ratings |
A car brochure quoting 100 PS means 100 × 0.7355 = 73.55 kW, which is 98.6 hp, so “PS” and “hp” figures are not interchangeable. A 1.5-ton split AC removes 1.5 × 3.517 = 5.28 kW of heat from the room; the electricity it draws is much lower, typically a third to a quarter of that, depending on its efficiency.
Flow rate
| Conversion | Value |
|---|---|
| 1 m³/s (cumec) | 1000 L/s = 3600 m³/h = 35.31 cusec |
| 1 MLD (million litres per day) | 11.574 L/s = 41.67 m³/h |
| 1 cfm | 1.699 m³/h = 0.4719 L/s |
| 1 US gpm | 0.06309 L/s = 0.2271 m³/h |
Water supply projects in India are sized in MLD. A 10 MLD treatment plant handles 10,000,000 L / 86,400 s = 115.7 L/s on average, the figure you would use to size pumps and pipes (before applying the peak factor).
Indian land and weight units
| Unit | Equivalent | Note |
|---|---|---|
| 1 gaj (square yard, for plots) | 9 ft² = 0.8361 m² | Plot sizes in North India |
| 1 guntha | 1089 ft² = 101.17 m² = 1/40 acre | Maharashtra, Karnataka, Gujarat |
| 1 cent | 435.6 ft² = 40.47 m² = 1/100 acre | Kerala, Tamil Nadu |
| 1 acre | 43,560 ft² = 4046.86 m² = 0.4047 ha | National |
| 1 hectare | 10,000 m² = 2.471 acre | Official land records |
| 1 tola | 11.6638 g | Gold and silver; jewellers now mostly use 10 g |
| 1 quintal | 100 kg | Crop prices (MSP is quoted per quintal) |
The bigha is deliberately left out of the converter: it is about 809 m² in Himachal Pradesh, about 1,338 m² in West Bengal and about 2,529 m² (pucca bigha) in Rajasthan, and it varies even between districts, so no single factor is correct. Always convert a bigha using the value on the local land record.
Significant figures: how many digits to report
A conversion cannot make a measurement more precise. If a drawing says a pipe run is 12 ft, converting gives 12 × 0.3048 = 3.6576 m, but “12 ft” was only known to about the nearest foot, so report 3.7 m. Use the significant-figures selector in the converter to match your input: keep as many significant figures as the least precise number you started with. Exact factors (like 0.3048) never limit precision.
When unit errors caused real failures
- Mars Climate Orbiter (1999). Ground software supplied by one team reported thruster impulse in pound-force seconds while the navigation software expected newton seconds. The factor of 4.45 error accumulated over months and the spacecraft was lost on arrival at Mars on 23 September 1999.
- The “Gimli Glider” (1983). An Air Canada Boeing 767 was fuelled using a pounds-per-litre density factor when the new aircraft needed kilograms. It carried less than half the fuel required, ran dry at 41,000 ft, and the crew glided it to a landing at a disused air base in Gimli, Manitoba.
Both were caught by nobody because the numbers looked reasonable. The habit that prevents it is simple: write the unit next to every number in every step of a calculation, and let the units cancel.
Frequently asked questions
What is unit conversion?
Unit conversion is changing a measurement from one unit to another without changing the quantity, by multiplying by a conversion factor equal to 1, such as 1000 m / 1 km. The result describes the same physical amount in different units.
How do I convert N/mm² to MPa?
They are the same. 1 N/mm² = 1 N / 10−6 m² = 106 Pa = 1 MPa, so a steel yield strength of 250 N/mm² is 250 MPa.
Is 1 kgf/cm² equal to 1 bar?
No. 1 kgf/cm² = 0.980665 bar, so they differ by about 2%. Older Indian pressure gauges read in kgf/cm², newer ones in bar or MPa, so convert rather than assume.
What is the difference between kB and KiB?
1 kB (kilobyte) = 1000 bytes in the SI sense, while 1 KiB (kibibyte) = 1024 bytes. A “1 TB” drive holds 1012 bytes, which an operating system counting in binary units shows as about 931 GiB.
How do I convert km/L to L/100 km?
Divide 100 by the km/L figure. A car that gives 20 km/L uses 100 / 20 = 5 L per 100 km. The converter’s fuel economy option handles this reciprocal conversion, and mpg as well.
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