[Closed] how to work out % of incline.....?

The slope is the Tangent of the angle.

Slope is rise/run, and the % grade is 100 times the slope. So a slope of 1/1 would be a 100% grade, which is indeed a 45 degree angle.

So if you know the degree of the angle, just enter it into your scientific calculator then hit Tangent.

The Tangent of 39 degree angle is:
0.809784

That is the slope, now multiply by 100 to get the % grade.
80.9784 %

i know the distance between two points and the height difference

Or:

[url] http://www.wikihow.com/Make-a-Clinometer [/url]

the old 1 in 4 was much easier

What distance do you know, length of the slope or horizontal distance?

If it's the length of the slope then divide the slope by the height. The result will give you the Sine of the angle. Find Tangent of the same angle, multiply by 100 which will be the %.

If it's the horizontal distance then divide height by horizontal distance which will give you the Tangent of the angle, multiply by 100 to give the %.