Pipe Slope Calculator
SI
Imp
Imperial
Inputs
View results
Calculation mode
Use slope mode when the required pitch is known. Use invert mode when start and end elevations are measured.
Slope to fall/invert
Inverts to slope
Pipe run length
(L)
Horizontal run length along the pipe layout, not the sloped pipe centerline length.
ft
Pipe slope
(S)
Slope as fall divided by horizontal run times 100. 2.083% equals 1/4 in per foot.
%
End direction
Gravity drains usually fall from start to end. Use rise only for an elevation comparison or non-gravity layout.
End lower than start
End higher than start
Start invert elevation
(E1)
Invert elevation at the upstream or starting point. The datum can be arbitrary if only the relative change matters.
ft
End invert elevation
(E2)
Measured downstream or ending invert elevation.
ft
Results
Default result
Edit inputs
Fall over run
(dE)
0.4167
ft
Pass
falls from start to end
Also computed
End invert elevation
(E2)
99.5833
ft
Slope percent
(S)
Pass
2.083
%
falls from start to end
Slope per foot
(pitch)
Pass
0.25
in/ft
falls from start to end
Pitch ratio
(1:n)
48
1:n
1:48.0
Pipe angle
(theta)
1.193
°
Run length used
(L)
20
ft
Pipe profile
run
fall
0.25 in/ft
2.08% slope, 1:48.0 ratio
Method notes
3 notes
Geometry: fall = run x slope percent / 100, and slope percent = fall / run x 100.
Useful conversions: 1/8 in/ft = 1.04%, 1/4 in/ft = 2.08%, and 1/2 in/ft = 4.17%.
This is a layout calculator only. Final drainage and plumbing work still needs adopted code, local amendments, fixture loads, pipe material, cleanouts, venting, traps, site elevations and inspection requirements.
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