Concrete Calculator

A concrete calculator turns form measurements into a volume estimate for a slab, patio, driveway, wall, footing or column. It expresses the same volume in cubic feet, cubic yards and cubic meters, then helps estimate an order using optional allowance, bag yield and pricing.

Concrete is the complete material containing cement and aggregate; cement alone is not interchangeable with premixed concrete. This concrete mix calculator estimates finished volume. It does not design cement, sand, aggregate or water proportions.

Convert measurements to compatible units before multiplying. Rectangular volume is length × width × depth. The wall and rectangular-column modes use that same geometry with labels suited to the project.

For a cylinder, volume = π × (diameter/2)² × height. A circular slab uses its thickness in place of height. A hollow tube subtracts the inner cylinder from the outer one: π × (outer radius² − inner radius²) × height. Multiply any single-object result by its quantity.

All displayed formulas use your actual measurements converted to feet. Expand Show Calculation Steps to inspect each section, the combined volume, conversions, allowance, bags and cost.

1. Choose the project shape and measure the actual form or space to be filled.
2. Select a unit for each dimension. Feet, inches, feet plus inches, yards, meters, centimeters and millimeters are supported. Changing a unit preserves its physical measurement.
3. Set the number of identical objects. Use Multiple Areas for sections with different dimensions or shapes, and give each a useful name.
4. Check the geometric total, then enter any optional additional allowance.
5. Use a product’s finished bag yield or a ready-mix quote to estimate the purchase.

For an irregular footprint, calculate its area with the Square Footage Calculator and choose Known area × thickness here. Do not count overlapping slabs or shared footing intersections twice.

Consider a slab 12 feet long, 10 feet wide and 4 inches thick. Convert thickness first: 4 ÷ 12 = ⅓ foot. Then multiply:

12 × 10 × (4/12) = 40 ft³.

The footprint is 120 ft². Dividing volume by 27 gives approximately 1.48148 yd³, while multiplying by 0.028316846592 gives approximately 1.13267 m³. The main result rounds to 1.48 yd³; ordering calculations retain the underlying value.

These dimensions illustrate the formula. They are not a specification for slab thickness, reinforcement or load capacity.

Cubic yards = cubic feet ÷ 27. One cubic foot equals exactly 0.028316846592 cubic meters; one cubic meter is approximately 35.3146667 cubic feet. These factors convert volume, unlike an area conversion.

With metric inputs, length × width × depth in meters directly gives cubic meters. One inch is exactly 2.54 centimeters, and one foot is exactly 0.3048 meters. Each dimension selector handles those conversions independently, so a length in feet and a thickness in millimeters are compatible.

Use bags = ceiling(purchase volume ÷ finished yield per bag). “Ceiling” means round upward to a whole bag. Keep yield and purchase volume in compatible units. This calculator accepts cubic feet, cubic meters or liters for custom yield.

For the 40 ft³ slab with a chosen 10% allowance, purchase volume is 44 ft³. At an approximate 0.60 ft³ per bag, 44 ÷ 0.60 = 73.333… and the estimate is 74 bags. Their nominal combined yield is 44.4 ft³; the extra 0.4 ft³ comes from rounding to whole bags, not a second allowance.

Bag weight can be recorded in pounds or kilograms to estimate dry premix mass. It does not determine yield. Finished concrete density is a separate optional calculation and is never substituted for a manufacturer’s bag yield.

A chosen 4-inch thickness uses ⅓ ft³ of concrete per square foot. For a 10 × 10 ft example, 100 × ⅓ = 33⅓ ft³, approximately 1.23457 yd³. At a 0.60 ft³ bag yield and no allowance, round 55.555… up to 56 bags.

The required structural thickness depends on the intended use and site conditions. Enter the specification for your project rather than treating this example as design advice.

At 6 inches, thickness is 0.5 feet. The same 100 ft² footprint needs 50 ft³, approximately 1.85185 yd³, before allowance. At 0.60 ft³ per bag, that is 84 whole bags.

Increasing thickness from 4 to 6 inches increases volume by 50% when area is unchanged. A small thickness measurement error can materially change the order, so measure actual forms and varying depths carefully.

A rectangular footing uses length × width × depth × quantity. A circular footing uses π × radius² × depth × quantity.

For four circular footings with example diameter 12 inches and depth 24 inches, convert radius to 0.5 ft and depth to 2 ft. Total volume is 4 × π × 0.5² × 2 ≈ 6.28319 ft³. Calculate different footing sizes as separate sections.

These are quantity estimates only. Soil, loads, frost conditions, building codes and professional requirements determine structural footing dimensions.

A circular column 12 inches in diameter and 8 feet high contains π × 0.5² × 8 ≈ 6.28319 ft³. A rectangular column uses its two cross-sectional dimensions multiplied by height. Multiply by quantity for identical columns.

For a concrete tube, enter outer and inner diameters and the height. The inner diameter must be smaller. In Post hole mode, optionally subtract a round or square embedded post; square posts use their actual square cross-section and must fit across their diagonal inside the hole. Embedded depth may be less than hole depth when there is concrete beneath the post.

These approximate example yields are specific to QUIKRETE Concrete Mix, Product No. 1101. They do not describe every concrete brand or mix. Use the yield stated on your bag label if it differs.

For bagged concrete, multiply rounded-up bags by price per bag. An illustrative 74 bags at $6 each costs $444 before delivery and other charges. For ready-mix, an illustrative 2 yd³ at $150/yd³ costs $300. These prices demonstrate arithmetic and are not current supplier quotes.

Enter your quote, optional delivery charge and additional charges. The total adds those costs once. USD, PKR, GBP and EUR formatting is supported; changing currency does not convert a price or retrieve an exchange rate. Costs exclude labor, reinforcement and any fees or taxes you have not entered.

Ready-mix quotes commonly use a volume unit such as a cubic yard or cubic meter. Premixed bags use a whole bag count and product-specific yield. Both purchasing methods start from the same geometric volume and chosen allowance.

Supplier minimum loads, delivery access, waiting charges, batching increments and mixing or placement logistics can affect a real order. This tool does not apply supplier minimums or round ready-mix to a supplier’s order increment. Confirm those terms directly.

Uneven forms, excavation differences and placement losses can cause actual consumption to differ from ideal geometry. An optional allowance increases the estimated purchase quantity while leaving the physical slab or footing volume unchanged.

Purchase volume = geometric volume × (1 + allowance%/100). At 10%, 40 ft³ becomes a 44 ft³ purchase estimate. Multiple Areas applies that percentage once to the combined total, before calculating bags or ready-mix cost. No preset percentage guarantees sufficient material.

Dimensions are stored internally in feet without display rounding. Calculations use JavaScript double-precision numbers and π for circular shapes. Conversion factors follow exact international length definitions; decimals shown in results are rounded for readability. Bag counts round upward after allowing for machine-scale numerical noise at an integer boundary.

The calculator accepts up to 12 sections, whole quantities from 1 to 1,000,000 and allowances from 0% to 100%. Nonpositive dimensions, invalid yields and nonfinite or excessively large intermediate values are rejected. Custom prices and densities must be finite and valid. Calculations run locally without a supplier service.

Copy, print and CSV include each section’s converted dimensions, formula, quantity and volume plus the purchase assumptions. Finished concrete weight uses geometric volume and the entered density; dry premix mass uses bag count and dry package weight. They describe different materials and stages.

Quantity estimation does not certify structural thickness, load capacity, concrete strength, reinforcement, soil suitability or building-code compliance. Seek the professional guidance appropriate to the construction decision.

Reference: QUIKRETE 1101 technical data: finished bag yields and approximate unit weight; QUIKRETE project calculators and yield guidance.