Grade & Fall Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the start and end RL.
- Enter the horizontal distance.
- Press Calculate.
How it works
Grade = (start RL − end RL) ÷ horizontal distance, shown as a percentage and a ratio. A positive value is a fall, negative is a rise.
Worked example
100.0 to 98.5 over 30 m. 1.5 m fall = 5% grade = 1:20.
Frequently asked questions
What grade do drains need?
It varies by pipe size and code, but common minimums are around 1% (1:100). Always check local standards.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.