Post Hole Concrete Calculator

Calculate one post hole as a cylinder: π × radius² × depth. Multiply by the number of holes, subtract any buried post volume if you want a tighter estimate, add waste, then convert the total volume into bags.Calculate one post hole as a cylinder: π × radius² × depth. Multiply by the number of holes, subtract any buried post volume if you want a tighter estimate, add waste, then convert the total volume into bags.

It depends on hole diameter, hole depth, post size, and bag yield. A common 12 inch diameter by 30 inch deep hole is about 1.96 ft³ before subtracting the post. With a 4×4 post and 10% waste, it is roughly four 60 lb bags per hole when using 0.45 ft³ bags.It depends on hole diameter, hole depth, post size, and bag yield. A 300 mm diameter by 750 mm deep hole is about 0.053 m³ before subtracting the post. With a 100 mm post and 10% waste, it is roughly four 20 kg bags per hole when using 0.010 m³ bags.

Yes if the post takes up meaningful space in the hole and you want a closer bag estimate. Leaving subtraction off is more conservative and may be useful when holes are irregular or over-dug.Yes if the post takes up meaningful space in the hole and you want a closer bag estimate. Leaving subtraction off is more conservative and may be useful when holes are irregular or over-dug.

No. This estimates concrete quantity only. Post depth, frost line, wind exposure, guardrail loads, utilities, drainage, and local code must be checked before digging or setting posts.No. This estimates concrete quantity only. Post depth, frost line, wind exposure, guardrail loads, utilities, drainage, and local code must be checked before digging or setting posts.