Calculators · Inside the building

Pipe fall calculator

How much a run drops end to end — and what grade that is.

How it is worked out

length × slope per foot = total fall in inches

What it assumes

The plumbing code sets the MINIMUM: ¼ in per foot for pipe 2½ in and smaller, ⅛ in per foot for 3 in and larger (IPC 704.1).
Too flat and solids stall. Too steep and the water outruns them — the same stoppage from the other direction.
This is arithmetic, not an approval. Your local code and your inspector have the final word, and amendments vary by county.

This is the same calculator that is in your Hub

Nothing on this page is a demo of the real thing — it runs the identical code. What a TradeForge account adds is everywhere the number then goes: saved against the job it belongs to, dropped straight onto a quote, and priced at a rate built from your own overhead instead of a guess.

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