Jobsite estimating

How much concrete? Down to the bag.

Six volume calculators — slab, footing, column, post holes, steps and curb — each giving cubic yards, cubic metres and the exact bag count for 40, 60 and 80 lb or 25 and 30 kg mixes, with a waste allowance. Plus 19 mix-ratio references and 179 worked examples.

Calculate a slab Mix ratios

27 ft³

In a cubic yard — the base of every count

0.60 ft³

Yield of an 80 lb bag of premix

179

Worked examples, each with its bag count

Concrete, mortar, grout & render ratios

Volume calculators

Pick the pour

Every calculator is free and works in feet, inches, metres or centimetres.

SlabConcrete slabPatios, floors, driveways and pads — length × width × thickness.FootingConcrete footingStrip and spread footings — length × width × depth.ColumnColumn & sonotubeRound columns and sonotube piers — π·r²·height.Post holesPost holeFence and deck post footings — hole volume, less the post.StepsConcrete stepsSolid poured stairs — stacked step cross-sections × width.CurbCurb & gutterCurbs and curb-and-gutter — cross-section × run.

Worked examples

Straight to a common job

The sizes people look up most, already calculated.

Concrete for a 10×10 ft slab, 4 in thick1.23 yd³56 × 80 lb bags Concrete for a 12×12 ft slab, 4 in thick1.78 yd³80 × 80 lb bags Concrete for a 20×20 ft slab, 6 in thick7.41 yd³334 × 80 lb bags Concrete for a 12 in sonotube, 4 ft tall0.12 yd³6 × 80 lb bags Mortar mix ratio for brickMortar Concrete mix for a drivewayConcrete mix

Reference

Mix ratios, rebar and cure times

Nominal concrete strength classes with their PSI and MPa, the four ASTM C270 mortar types and where each belongs, plus grout, render and screed proportions. A rebar grid estimator, the water-cement ratio explained, and how long concrete really takes to cure — all free, no sign-up.

Browse mix ratios Rebar estimator Water-cement ratio Cure time

Estimates for planning. MixRatio computes material quantities from standard volume formulas and typical bag yields. Structural and load-bearing work must follow your local building code and a qualified engineer's specification.