T-Post Calculator
Calculate how many steel T-posts you need for a wire or field fence from its perimeter and post spacing, plus total material cost.
How this calculator works
T-posts are line posts for wire and field fence, spaced along the perimeter rather than set individually by hand-dug hole. This calculator treats your fenced area as a rectangle, computes the perimeter, divides by your chosen post spacing, and adds one closing post — the same perimeter-based logic used for wood fence posts, just at wire-fence spacing.
Formula: Perimeter = 2 × (Length + Width). Posts = floor(Perimeter ÷ Spacing) + 1.
Worked example
A 100 ft × 100 ft fenced field, with T-posts spaced 8 ft apart:
- Perimeter: 2 × (100 + 100) = 400 ft
- Posts: floor(400 ÷ 8) + 1 = floor(50) + 1 = 51 posts
- At $8/post, that’s $408.00.
Coverage reference
| Area | Posts (8 ft spacing) |
|---|---|
| 50 x 100 ft | 38 posts |
| 100 x 100 ft | 51 posts |
| 200 x 100 ft | 76 posts |
How to measure your fence line
Walk the perimeter and measure the two distinct side lengths of your rectangular field or pasture in feet. Then decide spacing based on your wire type: tighter 8-foot spacing for woven or welded wire that needs more support between posts, or 10-12 feet for high-tensile smooth wire strung tight enough to span longer gaps. Remember this count is line posts only — corner, end, and gate posts are a separate, heavier-duty item.
Frequently asked questions
What spacing is typical for T-posts in a wire or field fence?
8 feet is a common baseline for woven wire and welded wire field fence, though many installers run T-posts at 10-12 feet when the fence uses several strands of high-tensile smooth wire, since the wire itself carries more of the load between posts. Adjust the spacing field to match your fence style.
Do T-posts need to be set in concrete?
No — T-posts are driven directly into the ground with a manual or gas-powered post driver, typically 18-24 inches deep depending on soil and fence height. Concrete is reserved for the wood or pipe corner, end, and gate posts that anchor the wire's tension.
Do I still need wood or pipe corner posts if I'm using T-posts?
Yes. T-posts are line posts only — they hold the fence's shape between anchor points but aren't strong enough to resist the pulling tension of stretched wire. Corners, ends, and gate openings still need a braced wood or pipe post set in concrete, which this calculator doesn't estimate separately.
What length T-post should I buy?
Add about 2 feet to your fence's above-ground height for the portion driven into the ground. A 4-foot fence typically uses 6-foot T-posts, while taller deer or livestock fencing often calls for 7- or 8-foot posts.
Can this calculator handle a single straight fence line instead of an enclosed perimeter?
This tool is built for an enclosed rectangular run and computes a full perimeter from two side lengths. For one straight line of fence, the simpler formula is posts = floor(run length ÷ spacing) + 1 — enter your run length as one side and set the other side to 0 to approximate it.
Estimates only. Verify quantities with your supplier before purchasing.