How to figure yards of concrete
Ready-mix is sold by the cubic yard (27 cubic feet). Measure each pour in feet, convert thickness from inches to feet, multiply, divide by 27, then add 5% to 10% extra.
Example
A 12 × 12 ft pad, 6 inches deep: 12 × 12 × 0.5 = 72 ft³ ÷ 27 = 2.67 yd³, or about 2.93 yd³ with 10% waste.
Ready-mix delivery tips
- Standard trucks carry about 10 cubic yards.
- Many suppliers charge a short-load fee on small orders, often under 4 to 5 yards.
- Order in ¼ yard increments and confirm pump or chute access.
Pouring a plain slab? Use the dedicated slab calculator. Small job? Check how many bags you need instead.
Real example: a 24 × 24 ft two-car garage floor
A homeowner measures a two-car garage at 24 ft by 24 ft and wants a 5 inch floor. They want to know: how much concrete do I need, and will one truck do it?
| Step | Math | Result |
|---|---|---|
| 1. Cubic feet | 24 × 24 × (5 ÷ 12) | 240 ft³ |
| 2. Cubic yards | 240 ÷ 27 | 8.89 yd³ |
| 3. Add 10% waste | 8.89 × 1.10 | 9.78 yd³ |
| 4. Trucks | 9.78 ÷ 10 yd per truck | 1 truck, order 10 yd³ |
The margin is thin: 9.78 yards on a 10 yard truck. That is a good sign for ordering, but if your subgrade is rough, ask the dispatcher about adding a quarter yard in case. Ordering 10 keeps you to one delivery, one crew and one finishing window.
Quick reference: yards per 100 square feet
| Thickness | Cubic yards per 100 ft² |
|---|---|
| 4 in | 1.23 |
| 5 in | 1.54 |
| 6 in | 1.85 |
Use this to sanity-check any answer. A 500 ft² slab at 4 inches should land near 6.2 yards before waste, so if your number is wildly different, re-check your units.
Common unit slip-ups
- Mixing inches and feet. Convert thickness to feet (divide by 12) before multiplying.
- Using yards for length. Everything stays in feet until the final ÷ 27.
- Forgetting multiple pours. Use the quantity field if you have, say, four identical footings.
Once you have your yardage, turn it into a budget with the concrete cost calculator. For a flat patio or driveway, the slab calculator adds a cost estimate directly, and for small jobs you may prefer bagged concrete. Prefer your phone on site? Get the free concrete calculator app.
Frequently asked questions
How many cubic feet are in a yard of concrete?
One cubic yard equals 27 cubic feet.
How do you calculate how much concrete you need?
Multiply length by width by thickness in feet, then divide by 27 to get cubic yards.
How much does a concrete truck hold?
A standard ready-mix truck typically carries about 10 cubic yards, though some hold less.
What is the minimum concrete order?
Minimums vary by supplier. Many deliver 1 yard or more but charge short-load fees on small orders.
Take the calculator to the job site
Free concrete calculator app for iPhone and Android.
Google Play App Store