Quick answer

4 inch 10x10 slab 56 80-lb bags before waste
With 10% waste About 62 80-lb bags
Ready-mix order About 1.36 yd3 with 10% waste
Cost basis $5 per 80-lb bag, $150/yd3 ready-mix

10x10 slab bag count by thickness

Use this table when the slab footprint is fixed at 10 ft by 10 ft. The order and cost columns include 10% extra material.

Scenario Dimensions Base volume 80-lb bags Ready-mix with 10% Bagged with 10%
Thin utility pad Not a normal structural slab thickness; use only when appropriate. 10 ft x 10 ft x 2 in 0.62 yd3 28 bags before waste 0.68 yd3 / $102 31 bags / $155
Light pad Sometimes used for very light pads, but 4 inches is more common. 10 ft x 10 ft x 3 in 0.93 yd3 42 bags before waste 1.02 yd3 / $153 46 bags / $230
Standard slab Common shed, patio, and utility pad thickness. 10 ft x 10 ft x 4 in 1.24 yd3 56 bags before waste 1.36 yd3 / $204 62 bags / $310
Heavier pad Extra thickness for heavier use or site requirements. 10 ft x 10 ft x 5 in 1.55 yd3 70 bags before waste 1.70 yd3 / $255 77 bags / $385
Hot tub or heavy pad Often ready-mix territory because bags become labor-heavy. 10 ft x 10 ft x 6 in 1.86 yd3 84 bags before waste 2.04 yd3 / $306 92 bags / $460

Interactive calculator

Concrete bag calculator

Use the calculator below when your slab is not exactly 10x10, or when you want to compare 40-lb, 50-lb, 60-lb, and 80-lb bags.

Enter length and width in feet, thickness in inches.

Use Area when you already know square footage. Ramp uses different start and end thicknesses.

Quick estimates
Component templates

Suggested waste for this setup: 5-10%. Regular flatwork usually needs enough margin for forms, grade variation, and small measurement errors.

Cost planning uses the selected order unit. Delivery, short-load fee, and labor are extra.

Advanced cost

Labor range uses $4-$8 per ft² as a planning range.

Multi-section estimate

Add irregular areas, aprons, landings, or pads and BuilderCalc will total them.

Estimated concrete neededEnter dimensionsLength, width, and thickness are required before the estimate appears.
Example4 x 4 ft pad x 4 in = about 9 80 lb bags with 10% waste

Bag counts are rounded up. Check the exact yield on the product label before buying.

How to decide what to buy

Use bag count for buying, not only cubic yards

A cubic-yard answer is useful for ready-mix. A DIY bag job needs whole bags, waste, mixer capacity, and the lifting weight of each bag.

A 10x10x4 slab is already a large bag job

About 62 80-lb bags with waste means roughly 4,960 lb of dry material before water. That is possible, but placement speed and finish timing matter.

Thickness changes the answer linearly

A 6 inch slab uses 50% more concrete than a 4 inch slab with the same footprint. Do not choose thickness only to reduce bag count.

Material checklist

  • 80-lb bag count with 10% extra for buying
  • Alternative 60-lb and 50-lb bag counts from the calculator
  • Mixer, water source, screed, forms, base, joints, and curing plan
  • Ready-mix comparison if the bag count becomes too high

Cost assumptions

The table uses $150 per cubic yard for ready-mix and $5 per 80-lb bag. It is a planning comparison, not a delivered quote.

  • At $5 per 80-lb bag, 62 bags is about $310 before tool rental or delivery.
  • At $150 per cubic yard, 1.36 ready-mix yards is about $204 before delivery, short-load, and local fees.
  • Bagged concrete can still be cheaper for access-limited jobs, but the labor is real.

Common mistakes

  • Buying the exact no-waste bag count.
  • Ignoring the printed yield on the exact product bag.
  • Trying to hand-mix a full slab with too small a crew.
  • Using 3 inches when the project really needs a 4 inch or thicker slab.

Formula and methodology

Volume in cubic feet equals length x width x thickness in feet. Cubic yards equal cubic feet / 27. An 80-lb premix bag is estimated at 0.60 cubic feet. Ready-mix order size and bagged cost use a 10% buying allowance for field variation.