How to Calculate the Lumber Requirements for a Fence

If you have a moderate grasp of basic carpentry techniques and a back strong enough for digging holes, you can save money by building your own wood fence. You could lose a significant portion of those savings by ordering more lumber than you need, though. Moreover, ordering too little can result in extra trips to the lumberyard, and you may miss out on quantity discounts for the extra lumber you have to buy. To accurately estimate your lumber requirements, you have to take into account the length of the fence as well as its design.


Lay out the perimeter of the fence and mark the corners with stakes. Measure the distance between each pair of corners with a 100-foot tape measure. Add these distances to get the total length of the fence. For example, a fence with four equal sides of 50 feet each has a total length of 200 feet.


Calculate the number of posts you need. This depends on the post spacing, which in most cases is 8 feet. Divide each section by the post spacing to get the number of posts in that section, then add the posts in all sections. A 200-foot fence with equal sides needs six posts spaced by 8 feet per side, for a total of 24. (50 ÷ 8 = 6.25, so 6 posts each side.) If you're using panels, and the spacing must be exact, you may have to adjust. If the sides are 50 feet long, adjusting them to form 48-foot sides allows exact 8-foot spacing between posts.


Multiply this number of posts by 1 1/2 times the height of the fence to account for the fact that 1/3 of the length of each post should be buried for fence stability. This gives you the number of linear feet of post material you need. For a 6-foot fence, each post should be 9 feet long, and if there are 24 of them, you need 216 linear feet of post material.


Determine the amount of railing material you need by multiplying the total length of the fence by 2. This accounts for a top and bottom railing, which is usually constructed with 2-by-4-inch lumber. If your design calls for more railings, multiply by the appropriate number. A 200-foot fence therefore needs 400 linear feet of railing.




Add 10 percent to each lumber amount you calculate. This accounts for the gate, as well as waste, mistakes and other contingencies.

Things You Will Need

  • Stakes
  • 100-foot tape measure



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