Slope Calculator

Calculate slope as a percentage, ratio, or degrees.

Mason ReidFounder and Lead Estimator at MeasureThen

Last updated 2026-08-21

What Is a Slope Calculator?

The slope calculator turns rise and run into a slope percentage, a ratio like X in 12, and an angle in degrees. It is used for grading, drainage, driveways, ramps, and roof pitch. Homeowners and DIYers use it to check that ground slopes away from a foundation or that a path drains properly.

How It Works

Slope % = Rise ÷ Run × 100. Ratio = Rise ÷ Run × 12 (in 12). Angle = atan(Rise ÷ Run).

Example

6 ft of rise over 100 ft of run: 6% slope, 0.7 in 12, 3.4°.

How to Calculate

Measure the rise, the vertical change, and the run, the horizontal distance, using the same units.
Enter both numbers. A rise of 6 ft over a run of 100 ft returns a 6% slope.
Read the angle in degrees, which is about 3.4° for that example.
Check the X in 12 ratio, which describes the rise per foot of run. That gives 0.7 in 12.
Compare against the minimum you need, such as a 5% grade for drainage away from a foundation.

Slope conversions and common uses

Slope	Degrees	Typical use
5% (6 in over 10 ft)	2.9°	Ground slope away from foundations
8.3% (1 in 12)	4.8°	Accessible ramp maximum
25% (3 in 12)	14.0°	Low slope roof edge
33% (4 in 12)	18.4°	Common roof pitch
100% (12 in 12)	45.0°	Steep roof pitch

Sources

Frequently Asked Questions

What is the difference between % and degrees?

Percent is the vertical rise per horizontal run × 100; degrees is the actual angle from horizontal.

What is a good drainage slope?

Ground should slope away from foundations at about 5% (2.4°) — roughly 6 in over 10 ft.

What does "X in 12" mean?

The rise in inches per 12 inches (1 ft) of run — the same notation roofers use for pitch.

Mason ReidFounder and Lead Estimator at MeasureThen

Mason Reid founded MeasureThen after two decades of hands-on work in construction and estimating. Across residential and light commercial projects, he sized concrete pours, framed walls, hung drywall, and priced out roofing, fencing, and deck work — learning the exact math that every job depends on. At MeasureThen he writes the formulas, checks every calculator against real-world assumptions, and makes sure each one is simple enough for a homeowner to trust and a contractor to use. When he is not measuring twice, he is helping projects stay on budget.

Every MeasureThen calculator uses simple, transparent formulas and standard industry assumptions drawn from common construction practice. We show the math behind each result and include worked examples so you can follow along and double-check the numbers. Results are estimates: materials, labor, and pricing vary by region and market, so always confirm important figures with a licensed professional and your local building codes.