Pipe Slope Calculator
Find pipe or channel slope from rise (drop) and horizontal run. Results include percent grade, slope ratio, inches per foot, and feet of fall per 100 feet.
Enter your values, then press Calculate.
How to calculate
Enter the elevation difference (drop) and the horizontal distance between the two points. Field shots are often in inches of drop over a tape distance in feet. The calculator converts both values to feet, then reports percent, ratio, inches per foot, and fall per 100 feet.
Formula
Slope = rise ÷ run. Percent grade = slope × 100. Inches per foot = (rise in inches) ÷ (run in feet). Ratio 1:X uses X = run ÷ rise. Feet of fall per 100 feet equals the percent grade when rise and run use the same length unit.
Common use cases
- Sewer and storm lateral slope checks
- Trench grade from hub elevations
- Converting 1/8 in per foot to percent
- Checking minimum pipe slope from plans
Worked example
Example: 6 inches over 50 feet is 1 percent
1. Convert rise to feet
6 in ÷ 12 = 0.5 ft
2. Decimal slope
0.5 ft ÷ 50 ft = 0.01 ft/ft
3. Percent grade
0.01 × 100 = 1 %
4. Inches of fall per foot of run
(0.5 ft × 12) ÷ 50 ft = 0.12 in/ft
Related calculators
- Percent Grade CalculatorConvert rise and run into percent grade, slope ratio, and feet per 100 feet.
- Bedding CalculatorEstimate pipe bedding cubic yards from length, width, and depth.
- Pipe Volume CalculatorCalculate internal volume of a circular pipe in cubic feet and gallons.
- Trench Excavation CalculatorConvert trench length, width, and depth into cubic yards of excavation.
FAQ
What is a 1% pipe slope?
A 1% slope drops 1 foot in 100 feet, or 0.12 inches per foot. A 6 inch drop in 50 feet is 1%.
How do I convert inches per foot to percent?
Divide inches per foot by 12, then multiply by 100. 1/8 in/ft is 1.042%, and 1/4 in/ft is 2.083%.
Does this replace the design slope on the plans?
No. Use it to check field measurements against the design. Minimum slopes for sewer and storm pipe come from the plans and the governing standard.
Disclaimer
These calculators are estimating tools for planning and field checks. They are not a substitute for approved plans, specifications, licensed professional engineering, or governing standards. Confirm densities, waste factors, and yields with your supplier and project documents.