Concrete Volume Calculator 2026: Cubic Feet, Yards & Meters

Volume Unit Conversion Reference

These are the exact conversion factors used by this calculator, reproduced here so you can sanity-check any result by hand or convert a number you already have.

The yard-to-meter conversion is exact because the international yard is defined as precisely 0.9144 meters. All other cubic-unit conversions in this table are derived directly from that definition and from 1 cubic yard = 27 cubic feet. See the concrete volume conversion chart for the full reference including cubic inches and liters.

The Formulas Behind Each Shape

Every concrete volume calculation reduces to the same idea: base area multiplied by height, with every dimension expressed in the same unit before you multiply. Where shapes differ is in how that base area is defined.

A rectangular slab uses length times width for its base area. A cylinder, like a concrete column or pier, uses a circular base area of pi times radius squared, where radius is exactly half the diameter, not the diameter itself. Using the full diameter in place of radius is the single most common error in cylindrical volume calculations, since it overstates the true volume by a factor of 4 (because the diameter squared is 4 times the radius squared). This calculator asks explicitly whether you are entering a diameter or a radius specifically to prevent that mistake.

A cone tapers to a point, so its formula carries a 1/3 multiplier: volume equals one-third times pi times radius squared times height. A frustum, a cone with the top sliced off flat, such as a tapered pier or a hopper base, needs both the top and bottom radius in the formula V = (pi x height / 3) x (R squared + R x r + r squared), where R is the larger radius and r is the smaller one. A sphere uses 4/3 x pi x radius cubed, and a hemispherical dome is exactly half that value.

Stairs are the outlier. Rather than a single base-area formula, the standard approach treats a stair run as stacked rectangular blocks, one per step, each block one riser taller than the last. The verified formula is Width x Rise x Run x N(N+1)/2, where N is the number of steps - this sums the volume of every step from the bottom to the top in one expression, without a separate triangular correction term that would double-count concrete already included in the stacked blocks.

Why Unit Consistency Is the Entire Game

Nearly every concrete volume error traces back to mixing units within one formula. Construction plans commonly specify length and width in feet but slab thickness in inches, since a 4-inch or 6-inch slab is easier to read than 0.333 or 0.5 feet. If that thickness gets multiplied directly as "4" instead of being divided by 12 first, the resulting volume comes out 12 times too large. This calculator converts every dimension to decimal feet before any multiplication occurs, which is why the thickness field for rectangular slabs is deliberately restricted to inches-only input rather than a mixed feet-and-inches field.

Common Volume Calculation Errors

• Multiplying inches directly instead of converting to feet: A 6-inch slab entered as "6" instead of "0.5 ft" produces a volume 12 times too large. Always divide inches by 12 before multiplying, or use the inches-only thickness field this calculator provides for exactly that reason.
• Using diameter where the formula needs radius: The circular area formula is pi x r squared, not pi x d squared. Substituting diameter for radius overstates volume by 4 times, since doubling a squared value quadruples it.
• Dividing by 3 instead of 27 for yard conversion: Converting cubic feet to cubic yards requires dividing by 27 (3 x 3 x 3), not by 3. Dividing by 3 only converts a single linear dimension from feet to yards, not a cubic volume.
• Forgetting a waste factor entirely: Uneven subgrade, form deflection, and spillage routinely consume 5-10% of the calculated volume. Ordering the bare theoretical number with zero cushion is the most common reason for running short mid-pour.
• Double-counting volume on stair calculations: Adding a separate triangular "base slab" term on top of stacked rectangular step blocks counts some concrete twice. The stacked-block method (Width x Rise x Run x N(N+1)/2) already accounts for the full solid volume in one expression.

Ordering Concrete Once You Have a Volume

Ready-mix concrete in the United States is sold and delivered by the cubic yard, while many international specs, imported equipment references, and metric project drawings use cubic meters. This calculator's simultaneous three-unit output exists specifically so a project spanning both systems, or a user simply more comfortable in one, does not need a second conversion tool.

Bagged concrete is priced and labeled by weight (40, 60, or 80 lb bags), and the volume-to-bag conversion depends on the manufacturer's stated yield per bag, not a universal constant. The bag-count figure shown in this calculator's advanced options is a general reference only. For a full cost comparison between bagged and ready-mix concrete at your calculated volume, use the concrete bag calculator or check exact yields on the concrete bag yield chart.

Standard ready-mix trucks carry roughly 9-10 cubic yards per load. If your calculated volume approaches or exceeds that figure, plan for multiple truck loads or confirm your supplier's minimum order and short-load fee policy. See the ready-mix truck calculator and ready-mix truck load chart for typical capacity by truck type.