Your local building department can tell you the frost depth and any fence rules in your area.
How the fence calculator works
FenceCalc splits each run into sections no longer than the post spacing, rounding up. Posts are the sections plus one, minus one for each corner shared by two runs, plus one extra post per gate. Rails are sections × rails per section. Pickets are the fence length minus the gate openings, in inches, divided by picket width plus gap, rounded up.
Concrete per hole is the hole's volume minus the post's, from the top of a 6-inch gravel base (if you include one) to ground level, divided by the bag yield and rounded up to whole bags.
Typical wood fence specs
| Fence | Posts | Rails | Pickets |
|---|---|---|---|
| 4 ft picket fence | 4×4, 6 ft long, 6–8 ft apart | 2 per section | 1×4, 2–3″ gaps |
| 6 ft privacy fence | 4×4, 8 ft long, 8 ft apart | 3 per section | 1×6, no gap |
| Gate posts | 4×4 or 6×6, set deeper | — | — |
Concrete bag yields
| Bag | Yield |
|---|---|
| 40 lb | 0.30 ft³ |
| 50 lb | 0.375 ft³ |
| 60 lb | 0.45 ft³ |
| 80 lb | 0.60 ft³ |
Yields are the published figures for Quikrete fast-setting and standard concrete mixes. Results are estimates: buy a few spare pickets and a spare bag, and check local codes, frost depth, HOA rules and underground utilities (call 811 in the US) before you dig.
Frequently asked questions
How deep should a 4 ft fence post be?
At least about 1⅓ ft by the one-third rule, though 2 ft is common for stability.
How wide should a post hole be?
About three times the post width.
What is the frost line?
The depth the ground freezes to in winter. Posts set above it can be heaved out by frost.
Is FenceCalc free?
Yes, with no sign-up or ads.
Are my measurements saved?
Yes, in this browser only.