Free · Garden & fencing
Fence Posts & Spacing Calculator
Estimate fence post requirements from run length and spacing.
- Formula & worked example
- Private in your browser
- No signup
Your calculation
Enter enough known values to calculate the blanks.
How to use this calculator
- Enter the values you know in the units shown. Leave unknown values blank.
- Results update automatically as you type. Edit a result to calculate another value, or lock a value to keep it fixed.
- Reset restores the starting fields. A worked example appears below.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
Post counts depend on fence length, spacing and how endpoints are treated. Gates, corners and changes in direction can require posts beyond a straight-run estimate.
Bays = ceiling(length / maximum spacing); posts = bays + 1
Worked example
Enter these known values and leave the other values blank.
- Fence length
- 20 m
- Post space
- 2.5 m
- Fence height
- 2 m
- Rails per section
- 2
- Post shape
- Cuboid
- Post width
- 10 cm
- Post thickness
- 10 cm
- Number of posts
- 9
- Number of sections
- 8
- Post length
- 3 m
- Number of rails
- 16
- Concrete volume
- 0.72 m³
Assumptions and limitations
- Inputs must satisfy the validation rules. Editing a result can recalculate an earlier input; lock values you want to keep fixed.
Common questions
What does this fence post calculation tell me?
Post counts depend on fence length, spacing and how endpoints are treated. Gates, corners and changes in direction can require posts beyond a straight-run estimate.
Can I calculate a different unknown?
Yes. Clear that field and enter the other known values. The calculator uses the available inverse equations.
References
The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.
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