How to calculate how much wood you will need for a fence

Enclosing your property with a wood fence provides security and privacy. There are different styles of wood fence construction varying in structural quality and aesthetic value. In most cases, deciding to build a monster fence with 15 by 15 cm (6 by 6 inch) post or a more standard 10 by 10 cm (4 by 4 inch) post is more a matter of how you want the fence to look. No matter how you intend to build the fence, determining the amount of building materials you need for the project always follows the initial layout and design.

Design the fence. Determine the type of construction, the size of post you'll be using, the slat pattern and the way in which the pieces interrelate. A simple construction type, for example, involves 10 by 10 cm (4 by 4 inch) post separated by 2.4 m (8 foot) stud rails. The studs are then covered by vertically placed cedar fence slats.

Measure the perimeter of the fence. Walk the path of the fence with a measuring tape adding up the lengths. Calculate the total fence perimeter.

Calculate the number of posts by dividing the overall perimeter length in metres by 2.4 (8 feet).

Calculate the number of rails by subtracting one from the number of posts and multiplying that number by two. For example, if you calculated you need 19 posts, 19 minus 1 is 18 and 18 multiplied by 2 is 36; in this example, you would need 36 rails.

Calculate the slats by first calculating how many slats are needed to fill one 2.4 m (8 foot) section. Divide 240 cm (96 inches) by the width of slat you intend to use; this is the number of slats per section. For example, if you use 11.2 cm (4 1/2 inch) wide slats, 240 cm (96 inches) divided by 11.2 cm (4.5 inches) is 21.428; in this example, you would need 22 slats per section. Subtract one from the number of posts to determine the number of sections and multiplying that number by the number of slats needed to fill one section. For example, if you determined the fence will have 18 sections and 22 slats per section, you would need 396 slats.


Order extra material; having a few extra posts, rails and slats on hand allows for breakage, lumber placement and section options.

Things You'll Need

  • Measuring tape
  • Paper
  • Pencil
  • Calculator
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About the Author

JL Wilson has worked in the construction industry for nearly 20 years. During that time, he labored as a carpenter, cabinetry door and millwork foreman, installer, designer, and account manager. He has designed, built, and installed projects as simple as a single jewelry box and as complicated as integrated swimming pool/waterfall complexes. Wilson primarily writes for eHow and Answerbag.