Concrete Calculator
Cubic yards and 40–80 lb bags for slabs, footings, round columns and post holes.
Free construction calculators · US & metric
Plan smarter. Build with confidence.
Every answer shows its work.
Estimate concrete, post holes and fence materials from your own measurements, with the formula behind every number.
Quick concrete estimate
LiveConcrete needed1.36 cu yd
62 × 80 lb bags
incl. 10% extra
incl. 10% extra
Calculators
Each one tested against worked examples and unit conversions.
Concrete Slab Calculator
Ready-mix volume and cost for patios, driveways and shed bases.
Fence Calculator
Posts, rails, pickets or panels, post concrete and material cost for a straight run.
Coming nextRoofing · Decking · Flooring · Painting
Why it’s different
Every answer shows its work
You shouldn’t have to trust a black box with your shopping list. Each result comes with the formula, your numbers in it, and the assumptions behind it, so you can check it before you buy.
- Real geometry. Round post holes are round, the post’s own volume can be subtracted, and fence panels have a fixed width.
- Checked numbers. Bag yields match the manufacturer’s data sheet, and every formula has automated tests.
- Tape-measure input. Type
10' 6"or5 1/2, or switch to metric and your numbers convert. - Take it with you. Copy a link to your result or print a shopping list.
Worked example · 12 fence posts
- π × radius² × depth (in feet)
- π × 0.4167² × 3 = 1.636 cu ft
- − post: 0.2917² × 3 = 0.255 cu ft
- = 1.381 cu ft per hole
- × 12 holes = 16.572 cu ft
- + 10% waste = 18.23 cu ft
- ÷ 27 = 0.675 cu yd
- ÷ 0.6 cu ft per bag = 30.38 → 31 bags
Buy31 × 80 lb bags
Guides
Plain-English walkthroughs of the math behind each calculator.
How Much Concrete Do You Need?
Measure your pour, convert to cubic yards, add a sensible margin and decide between bags and ready-mix — with worked examples.
How to Calculate Fence Materials
Work out posts, rails and boards for a straight wood fence run, avoid the classic off-by-one post mistake, and build a shopping list.
How to Estimate Concrete Slab Costs
Turn slab dimensions into a material budget: volume, ready-mix pricing, delivery charges and the costs people forget to include.