About this tool
Estimate the gravel for a French drain trench with a perforated pipe.
Gravel volume = trench length × width × depth − pipe volume (π·r²·length). Tonnes = volume × gravel density.
Formula: V = L·W·D − πr²L
Example: Trench length (m) = 15, Trench width (cm) = 30, Trench depth (cm) = 45, Pipe diameter (cm) = 10, Gravel density (t/m³) = 1.6 → Gravel volume (m³) = 1.907, Gravel weight (t) = 3.05.
Typical drainage gravel weighs about 1.6 t/m³.
Quick steps
- Enter your values — every field shows its unit.
- Press Calculate (or Try an example to see how it works).
- Read the results and copy them if you need them elsewhere.
The calculation runs in your browser. Nothing you type is sent to 1CLIK.
FAQ
How does the French Drain Calculator work?
Gravel volume = trench length × width × depth − pipe volume (π·r²·length). Tonnes = volume × gravel density.
What should I keep in mind?
Typical drainage gravel weighs about 1.6 t/m³.
Is my data sent anywhere?
No. The numbers stay on your device; the page only shows the result.