Concrete & Masonry Calculators
Plan a pour from start to finish: size the slab or footing, decide between bags and a ready-mix truck, lay out the rebar and price the job.
7 calculators · Imperial and metric · Free
Concrete Slab Calculator Slabs, pads, footings, round pads, columns and steps in cubic yards, m³ and bags. Concrete Bag Calculator How many 40, 50, 60 or 80 lb bags (or 20–40 kg bags) a job needs. Post Hole Concrete Calculator Concrete and gravel per post hole, with the post volume subtracted. Sonotube Calculator Concrete for round form tubes and bell footings, per tube and in total. Concrete Cost Calculator Compare DIY bags, ready-mix delivery and hiring a pro with your local prices. Rebar Calculator Bars each way, laps, stock bars to buy and weight, with a layout diagram. Concrete Block Calculator Blocks, courses, mortar and core-fill grout for a block wall, minus openings.
Which concrete calculator do I need?
| Project | Start with | Then |
|---|---|---|
| Patio, shed base or garage slab | Concrete slab calculator | Gravel base, rebar, cost |
| Fence, mailbox or pergola posts | Post hole concrete calculator | Bags, drainage gravel |
| Deck or porch footings | Sonotube calculator | Bags, rebar |
| Block retaining or garden wall | Concrete block calculator | Footing, rebar |
| Concrete steps | Concrete slab calculator (Steps) | Bags |
| Small repair or pad | Concrete bag calculator | – |
Planning a concrete pour, step by step
- Measure and decide the thickness. Four inches (100 mm) suits patios and paths; driveways usually need 5 to 6 inches.
- Prepare the base. Most slabs sit on 4 inches or more of compacted gravel. Work out the stone with the gravel calculator.
- Plan the reinforcement. Lay out mesh or rebar so it sits near the middle of the slab, supported on chairs.
- Calculate the volume with waste. Order 5–10% extra so you never run short mid-pour.
- Choose bags or ready-mix. Under about one cubic yard, bags are manageable. Beyond that, a truck is usually easier and often cheaper.
- Check the weather. Avoid pouring in freezing conditions or extreme heat, and keep the slab damp while it cures.
Concrete quantities at a glance
- 1 cubic yard = 27 cubic feet = 0.765 m³.
- An 80 lb bag makes about 0.60 ft³, so a cubic yard is about 45 bags (60 bags of 60 lb mix).
- One cubic yard covers about 81 sq ft at 4 inches thick, or 54 sq ft at 6 inches.
- One cubic meter covers 10 m² at 100 mm thick.