Gradient calculator

How the calculator works

Type the length of the road and the height it gains. The calculator divides the height by the length to give the slope in per cent. A slope of 5% means the road goes up 5 m for every 100 m you ride.

If you know the rise and the run instead, pick that choice. Rise is how far up the road goes. Run is the flat distance across, as you would measure it on a map.

Per cent and degrees

Road signs and climb guides give the slope in per cent. Per cent compares how far up you go with how far along you go. Degrees measure the angle of the road, like the angle you would draw with a protractor.

The two numbers are not the same, and per cent is always the bigger one. A 10% road has an angle of about 5.7 degrees. A road at 45 degrees would be 100%, because it would go up as far as it goes along.

How steep a road feels

The calculator puts the slope into one of five bands, from flat to steep. The Couch to Climb app uses the same bands to colour the road on its climbs. Flat is under 2%, and steep is 11% and over. The table next to the answer shows all five.

An average can hide the hard parts. A climb that averages 6% may have short stretches at 10% or more, so look at the steepest part too.

Where the numbers come from

Slope in per cent is the rise divided by the run, times 100. To turn that into degrees, the calculator uses the inverse tangent, a button on most science calculators. Both sums come from the Wikipedia page on grade.

Climb guides and bike computers divide the height by the length of the road, not the flat distance. On real roads the gap is tiny. On a 10% road it changes the answer by less than a tenth of a per cent.