# Unit conversion

Unit conversion looks trivial and fails expensively: treating kN as kgf, MPa as kg/cm², or a 1:2 slope as 2%. Any one of those puts the answer out by an order of magnitude. These converters are grouped by physical quantity and include the units that really do appear on local drawings, including kilogram-force and the old engineering atmosphere.

Slope gets its own tool because it is the most misread. It has three forms — degrees, percent and ratio 1:n — and 30° is 57.7% and 1:1.73, not 1:30 and not 30%. Code limits for roofs and drainage falls are written in percent while drawings often show a ratio, and a mistake between them is a straight non-compliance.

- Category page: https://jianzhujisuan.com/en/c/unit-conversion
- Data checked: 2026-10-25

## Tools in this group

- [Slope Converter](https://jianzhujisuan.com/en/slope-converter): Enter rise and run to get the slope as a percentage, in degrees, as a ratio and as rise per metre.
- [Length Unit Converter](https://jianzhujisuan.com/en/unit-length): Metres, millimetres, feet and inches — every unit shown at once.
- [Area Unit Converter](https://jianzhujisuan.com/en/unit-area): Square metres, hectares, mu and square feet — all units at once.
- [Volume Unit Converter](https://jianzhujisuan.com/en/unit-volume): Cubic metres, litres, gallons and cubic feet — all units at once.
- [Weight Unit Converter](https://jianzhujisuan.com/en/unit-weight): Tonnes, kilograms, jin and pounds — every unit at once.
- [Pressure Unit Converter](https://jianzhujisuan.com/en/unit-pressure): MPa, kPa, bar, psi and kgf/cm² — every unit at once.
- [Force Unit Converter](https://jianzhujisuan.com/en/unit-force): kN, N, tonne-force, kgf and lbf for loads and lifting.
- [Temperature Converter](https://jianzhujisuan.com/en/unit-temperature): Celsius, Fahrenheit and Kelvin, with site temperature references.
- [Angle Converter](https://jianzhujisuan.com/en/unit-angle): Degrees, minutes, radians and slope percent, all at once.
- [Flow Rate Converter](https://jianzhujisuan.com/en/unit-flow): m³/h, L/s, L/min and GPM — every unit at once.
- [Power and Heat Converter](https://jianzhujisuan.com/en/unit-power): kW, horsepower, kcal/h, BTU/h and tons of refrigeration.

## Questions

### How many kg/cm² is 1 MPa?

About 10.2 kgf/cm², commonly rounded to ten on site. Going the other way, 1 kgf/cm² is roughly 0.098 MPa. Do not confuse mass with force: kg is mass, kgf is force, and only kgf/cm² is a pressure. Concrete grade C30 means 30 MPa, about 300 kgf/cm².

### What angle is a 1:2 slope?

arctan(0.5) = 26.57°, which is 50% in percent terms. A 30° slope is 57.7% and 1:1.73. When a waterproofing code says the fall must be at least 2%, it means 20 mm per metre, about 1.15° — not 2°.

### How many litres in a cubic metre?

1 m³ = 1000 L. That applies to concrete, mortar and water volume alike. One tonne equals one cubic metre only for water at 1000 kg/m³; every other material needs its own density.