Work out how many bags a pour needs, by bag size, with the formula and assumptions shown below the tool.
Concrete bags job sheet · ProjectTallyKit.com
Your estimate
Fix the highlighted field to update the estimate. The figures below are for your last valid entry.
Buy 62 × 80-lb bags
Exact amount with waste: 1.358 yd³ (36.67 ft³)
- Concrete for 1 pour: 1.235 yd³ (33.33 ft³) before waste
- 10% waste added once, to the total
- Rounded up to whole bags. Each bag weighs 80 lb.
- 1 full pallet of 42 bags and 20 loose bags.
- You will lift 4,960 lb in total.
Or about 1.36 yd³ of ready-mix concrete
This is a material estimate, not a structural design. Thickness, reinforcement, sub-base and loads need site-specific advice.
| Bag size | Bags | Weight | Pallets + loose |
|---|---|---|---|
| 40-lb | 123 | 4,920 lb | 1 + 43 |
| 50-lb | 98 | 4,900 lb | — |
| 60-lb | 82 | 4,920 lb | 1 + 26 |
| 80-lb | 62 | 4,960 lb | 1 + 20 |
Bags per cubic yard, rounded up: 90 × 40-lb, 72 × 50-lb, 60 × 60-lb, 45 × 80-lb. Yields from the QUIKRETE Concrete Mix No. 1101 data sheet.
Least concrete left over: 5 × 50-lb + 58 × 80-lb leaves 0.01 ft³, against 0.08 ft³ with 98 × 50-lb.
Cost comparison
- Add your own bag or ready-mix prices under “Buying options and prices” to compare costs. Prices are never filled in for you.
What if
| Waste | Order | 80-lb bags | Cost |
|---|---|---|---|
| 5% | 1.30 yd³ | 59 | — |
| 10% | 1.36 yd³ | 62 | — |
| 15% | 1.42 yd³ | 64 | — |
| 20% | 1.49 yd³ | 67 | — |
Show the math with my numbers
- Pour 1 (slab): 10 ft × 10 ft × 4 in ÷ 12 = 33.33 ft³
- With waste: 33.33 ft³ × 1.1 = 36.67 ft³
- In cubic yards: 36.67 ft³ ÷ 27 = 1.358 yd³ (1.038 m³)
- Bags: 36.67 ft³ ÷ 0.6 ft³ per 80-lb bag = 61.11, rounded up to 62
- Pallets: 62 bags ÷ 42 per pallet = 1 full pallet and 20 loose bags
Shopping list
- Concrete mix, 80-lb bags62 bags (4,960 lb)
Calculations run in your browser. Your measurements are not sent to us.
How this estimate is calculated
This is a material estimate, not a structural design. Thickness, reinforcement, sub-base and loads need site-specific advice.
Before you buy
- Measure each pour. For post holes, measure the hole you will actually dig; holes are often wider at the top.
- Read the yield and weight on the bag you will buy, and ask your store how many bags are on a pallet; change them under “Bag options”.
- Check your vehicle’s payload before you load it, and plan help for lifting.
- For larger pours, add a ready-mix price to see where delivered concrete becomes cheaper.
- This estimate covers concrete only: not gravel, form tubes, reinforcement, tools or finishing supplies.
- Check permits, local code and utility locates before you dig or pour.
Formula
- Volume of each pour: slab L × W × T ÷ 12; footing or wall L × W × D; post hole (π × (D ÷ 2)² − post area) × depth; round column π × (D ÷ 2)² × H; square column L × W × H; solid stairs run × width × rise × n(n + 1) ÷ 2, plus landing × width × total rise. Pours are added up.
- Order volume = total × (1 + waste ÷ 100), applied once
- Bags = order volume ÷ bag yield, rounded up to a whole bag; weight = bags × bag weight
- Full pallets = bags ÷ bags per pallet, rounded down; the rest are loose bags
- Trips = total weight ÷ your payload, rounded up
Worked example
- Pour 1 (slab): 10 ft × 10 ft × 4 in ÷ 12 = 33.33 ft³
- With waste: 33.33 ft³ × 1.1 = 36.67 ft³
- In cubic yards: 36.67 ft³ ÷ 27 = 1.358 yd³ (1.038 m³)
- Bags: 36.67 ft³ ÷ 0.6 ft³ per 80-lb bag = 61.11, rounded up to 62
- Pallets: 62 bags ÷ 42 per pallet = 1 full pallet and 20 loose bags
| Case | Before waste | With waste | Exact bags | Bags to buy |
|---|---|---|---|---|
| Default example: slab 10 × 10 ft, 4 in thick, 10% waste | 33.33 ft³ | 36.67 ft³ | 61.11 × 80-lb | 62 × 80-lb |
| 1 yd³ (27 ft³), no waste | 27 ft³ | 27 ft³ | 45 × 80-lb | 45 × 80-lb |
| 4 post holes 9 in across and 2 ft deep, 3 in round posts, 10% waste | 3.14 ft³ | 3.46 ft³ | 5.76 × 80-lb | 6 × 80-lb |
| 3 solid steps, 7 in rise, 11 in run, 4 ft wide, 3 ft top landing, no waste | 33.83 ft³ | 33.83 ft³ | 56.39 × 80-lb | 57 × 80-lb |
This page recalculates each case with the same formulas as the calculator, and the same cases run as automated tests of the code.
| Bag size | Yield | Exact | Rounded up |
|---|---|---|---|
| 40-lb | 0.3 ft³ | 90 | 90 |
| 50-lb | 0.375 ft³ | 72 | 72 |
| 60-lb | 0.45 ft³ | 60 | 60 |
| 80-lb | 0.6 ft³ | 45 | 45 |
Rounding
Everything is calculated at full precision. Bags and trips are rounded up to whole numbers (after removing floating-point noise); full pallets are rounded down and the rest shown as loose bags. Volumes are never rounded up to whole yards.
Constants and sources
What this estimate does not cover
Not included: gravel under posts, form tubes, reinforcement, tools, delivery rules and taxes, and anything about whether a footing, post or stair design is suitable. Ask a local professional or your building department about design and code.
Last reviewed October 12, 2026. Next review due April 12, 2027.