Roof downpipe fitting inventory calculator

Calculate diagonal pipe centerline length and offset vertical drop with your own figures.

Your numbers

Use the units shown. Results update as you change valid inputs.

Use diagonal pipe centerline length and offset vertical drop to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Measured vertical inlet-to-outlet drop (mm)
5000
Required horizontal offset (mm)
400
Supplied offset bend angle to vertical (degrees)
45
Supplied total fitting vertical take-up (mm)
200
Supplied insertion allowance per pipe end (mm)
30
Diagonal pipe centerline length (mm)
565.685425
Offset vertical drop (mm)
400
Remaining straight centerline drop (mm)
4400
Diagonal cut with two insertions (mm)
625.685425
Offset bend fitting count
2

Try another scenario

Measured vertical inlet-to-outlet drop (mm)
5000
Required horizontal offset (mm)
600
Supplied offset bend angle to vertical (degrees)
45
Supplied total fitting vertical take-up (mm)
200
Supplied insertion allowance per pipe end (mm)
30
Diagonal pipe centerline length (mm)
848.528137
Offset vertical drop (mm)
600
Remaining straight centerline drop (mm)
4200
Diagonal cut with two insertions (mm)
908.528137
Offset bend fitting count
2
Calculation method

Calculation method

Diagonal pipe centerline length (mm)

b/math.sin(c*math.pi/180)

Offset vertical drop (mm)

b/math.tan(c*math.pi/180)

Remaining straight centerline drop (mm)

a-d-b/math.tan(c*math.pi/180)

Diagonal cut with two insertions (mm)

b/math.sin(c*math.pi/180)+2*e

Offset bend fitting count

2

Symbols and units
a
Measured vertical inlet-to-outlet drop (mm)
b
Required horizontal offset (mm)
c
Supplied offset bend angle to vertical (degrees)
d
Supplied total fitting vertical take-up (mm)
e
Supplied insertion allowance per pipe end (mm)

Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.

Assumptions & limits

Assumptions & limits

  • One two-bend offset with supplied fitting geometry; angle strictly 0–90° and remaining straight drop≥0. Actual cut allowances must follow product measurements. Supported limits: All numeric inputs must be finite. Only the explicitly described mathematical scenario is supported.
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