Slope and fall
Slope is written differently depending on the trade: 2 % on a sewer, 20 mm per metre on paving, 1 : 50 on a roof. It is the same slope — here you can convert between them.
Your numbers
Answer
Percent
2%
mm per metre
20mm/m
Degrees
1.15°
Ratio
1 : 50
Per mille
20‰
Height difference over 5 m
100mm
How to work it out
- 1mm/m = % · 10 = 20 mm/m
- 2° = tan⁻¹(2 / 100) = 1.15°
- 31 : x = 1 : (100 / 2) = 1 : 50
- 4Height difference = 5 m · 2 / 100 = 0.1 m = 100 mm
The formula
% = højde / længde · 100
The slope in per cent is the height difference divided by the horizontal length.
mm/m = % · 10 = ‰
2 % is 20 mm per metre — and the same as 20 per mille.
° = tan⁻¹(% / 100) · 1 : x = 1 : (100 / %)
The drawing is exaggerated for small slopes so it can be seen. The numbers are correct.
More: Workshop maths
- Material consumption including wasteNumber of boards or tiles and litres of paint from the area — with waste.
- Mix ratio1 : 50, percentages and dilution — how much of each for the amount you need.
- Density and weightThe weight of a plate, a bar or a tube — from dimensions and density.
- Unit priceCompare offers on price per kg, litre, metre or piece.