Unit conversion calculators

11 engineering unit converters: length, area, volume, weight, pressure and stress, force and load, temperature, angle, slope, flow and power. All the units that actually appear on drawings.

11 tools, most used first

◺Slope ConverterEnter rise and run to get the slope as a percentage, in degrees, as a ratio and as rise per metre.↔Length Unit ConverterMetres, millimetres, feet and inches — every unit shown at once.▭Area Unit ConverterSquare metres, hectares, mu and square feet — all units at once.◫Volume Unit ConverterCubic metres, litres, gallons and cubic feet — all units at once.⚖Weight Unit ConverterTonnes, kilograms, jin and pounds — every unit at once.◉Pressure Unit ConverterMPa, kPa, bar, psi and kgf/cm² — every unit at once.⇉Force Unit ConverterkN, N, tonne-force, kgf and lbf for loads and lifting.🌡Temperature ConverterCelsius, Fahrenheit and Kelvin, with site temperature references.∠Angle ConverterDegrees, minutes, radians and slope percent, all at once.⇢Flow Rate Converterm³/h, L/s, L/min and GPM — every unit at once.⚡Power and Heat ConverterkW, horsepower, kcal/h, BTU/h and tons of refrigeration.

What this group solves

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.

Unit conversion looks trivial and is in fact where site accidents come from: MPa against bar, kN against kgf, m³/h against L/s — one place out and you are a factor of ten or a hundred wrong. The only rule is to bring every parameter into one system before substituting into a formula, never convert midway through. That is exactly what these tools are for: do the conversion on its own, then feed the result back.

Which one for your case

Slope between percentage, degrees and ratio	Slope Converter
Length including feet, inches and Chinese chi	Length Unit Converter
Area including mu and hectares	Area Unit Converter
Volume including gallons and cubic feet	Volume Unit Converter
Mass including tonnes, jin and pounds	Weight Unit Converter
Pressure — MPa, bar, psi, kgf/cm²	Pressure Unit Converter
Force — kN, tf, lbf	Force Unit Converter
Temperature — °C, °F, K	Temperature Converter
Angle — degrees, radians, slope	Angle Converter
Flow — m³/h, L/s, L/min	Flow Rate Converter
Power — kW, horsepower, refrigeration tons	Power and Heat Converter

Where this group goes wrong

Mixing gauge units. 1 MPa = 10 bar = 10.2 kgf/cm² ≈ 145 psi. Grouting and pressure-test gauges come marked in either MPa or bar, and reading the wrong one can over-pressurise tenfold.
Treating kN as kg. 1 kN ≈ 102 kg at g = 9.8, so estimating 1 kN = 100 kg is 2% conservative — but treating 1 kN as 1 kg is out by a factor of 100. This is the classic fatal error in lifting plans.
Converting a temperature difference as if it were a temperature. A rise of 20 °C is a rise of 20 K but a rise of 36 °F — Fahrenheit differences multiply by 1.8 and must not carry the +32 offset.
Assuming slope percentage and degrees are linear. i = tan(θ)×100%: 2% is 1.15°, 5% is 2.86°, 10% is 5.71° and 30° is 57.7%. The approximation holds at small angles and falls apart past about 10%.

FAQ

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.

How do slope percentage and degrees convert?

i = tan(θ) × 100%, and θ = arctan(i/100). Common values: 1% → 0.57°, 2% → 1.15°, 5% → 2.86°, 10% → 5.71°, 15% → 8.53°, 30° → 57.74°. Drainage falls are often given in per mille (‰) and convert the same way.

How many kilograms of pressure is 1 MPa?

1 MPa = 1 N/mm² ≈ 10.2 kgf/cm². The site shorthand of '10 kilos of pressure' is strictly 0.98 MPa, so treating 1 MPa as about 10 kgf/cm² is conservative and fine for pressure testing. In psi, 1 MPa ≈ 145.04 psi.

How many square metres is one mu?

666.67 m², or 1/15 of a hectare. One hectare is 15 mu or 10,000 m², and 1 m² is 0.0015 mu. Land acquisition and temporary works use this a lot — do not confuse it with the acre (4046.86 m²).

What is 30 MPa of concrete in psi?

30 MPa ≈ 4351 psi, at 1 MPa = 145.04 psi. European and American drawings often specify concrete in psi or ksi — 4000 psi is about 27.6 MPa, so it sits between C25 and C30 on the Chinese grade scale.

Related data tables

Construction unit conversionsThe handful of conversions that actually get used, on one page — especially kN/kgf and MPa/kgf/cm², where most errors happen.

Other groups

Concrete Rebar Masonry Finishes Earthwork Temporary Works Construction Costing M&E Material weights Area and volume Code Lookup

Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.