Guide · Concrete
How Much Concrete Do I Need for a 16×16 Slab?
A 16×16 slab poured 4 inches thick needs 3.16 cubic yards of concrete — about 85.33 cubic feet. That’s the classic size for a big patio or small workshop floor. Add a 10% waste allowance for uneven subgrade and spillage, and plan for 3.48 cubic yards. Mixing bags instead of ordering ready-mix? That’s 190 sixty-pound bags before waste, or 209 with waste built in.
Those are the headline numbers. Below is the exact math so you can verify it, a chart covering other common slab sizes, and guidance on thickness, bags vs. ready-mix, and cost. If you’d rather skip the arithmetic, use our free concrete calculator — enter your slab dimensions and it returns cubic yards plus 40-, 60-, and 80-lb bag counts in seconds.
Get cubic yards and bag counts for your exact slab dimensions — free, no sign-up.
Use the interactive concrete calculator →Before waste. With a 10% allowance: 3.48 yd³, or 209 sixty-pound bags.
The math, step by step
= 16 ft × 16 ft × (4 ÷ 12) ft = 85.33 ft³
Cubic yards = 85.33 ÷ 27 = 3.16 yd³
- Convert thickness to feet. Four inches is 4 ÷ 12 = 0.333 ft.
- Multiply. 16 × 16 × 0.333 = 85.33 cubic feet.
- Convert to cubic yards. There are 27 cubic feet in a yard: 85.33 ÷ 27 = 3.16 yd³.
- Add waste. 3.16 × 1.10 = 3.48 cubic yards to order.
- Convert to bags. A 60-lb bag yields about 0.45 ft³: 85.33 ÷ 0.45 = 189.63, round up to 190 bags. With waste: 93.87 ÷ 0.45 = 208.59, round up to 209 bags.
Concrete needed for common slab sizes
Bag counts below are before waste and assume the standard 0.45 ft³ yield per 60-lb bag. Add 10% when ordering.
| Slab size | Thickness | Cubic feet | Cubic yards | 60-lb bags |
|---|---|---|---|---|
| 8×8 | 4″ | 21.33 | 0.79 | 48 |
| 8×8 | 6″ | 32 | 1.19 | 72 |
| 10×10 | 4″ | 33.33 | 1.23 | 75 |
| 10×10 | 6″ | 50 | 1.85 | 112 |
| 12×12 | 4″ | 48 | 1.78 | 107 |
| 12×12 | 6″ | 72 | 2.67 | 160 |
| 12×16 | 4″ | 64 | 2.37 | 143 |
| 16×16 | 4″ | 85.33 | 3.16 | 190 |
| 20×20 | 4″ | 133.33 | 4.94 | 297 |
| 24×24 | 4″ | 192 | 7.11 | 427 |
Check the yield printed on your product label — most US 60-lb concrete-mix bags state 0.45 ft³, but specialty mixes can differ.
How thick should a 16×16 slab be?
Four inches is the standard for patios, walkways, and shed floors — and it’s what every number on this page assumes. Go thicker (5–6 inches) for driveways or anything carrying vehicles or heavy equipment. Whatever the thickness, the slab should sit on at least 4 inches of compacted gravel sub-base (our gravel calculator handles the sub-base math), and most slabs benefit from reinforcement — wire mesh or rebar on chairs, sized for the load. Our rebar grid calculator estimates bar counts, laps, and weight for a slab grid.
Bags or ready-mix for a 16×16 slab?
A 16×16 slab at 4 inches needs 190–209 sixty-pound bags — roughly 5.7 tons of dry mix to haul, stage, and mix. 190 bags is 5.7 tons of dry mix. Order the truck — bags would cost more per yard and the pour would take days. Ready-mix suppliers have minimum-load charges (often 1–3 yards), so call ahead and confirm the short-load fee before you commit.
What does a 16×16 concrete slab cost?
Cost is just your volume times your local price. For bags: 209 bags × the per-bag price at your store. As a rough planning figure, sixty-pound bags commonly run about $4–$6 at US home centers, which puts bag material for this slab in the ballpark of $840–$1,250 — but treat that as a placeholder and check current shelf prices, which move by region and season. Ready-mix is typically quoted per cubic yard plus delivery, so get two quotes. Forming lumber, gravel sub-base, reinforcement, and labor sit on top of the concrete itself.
Pouring day: what to expect
If you go the bag route, know what you’re signing up for. A typical homeowner-grade 3.5-cubic-foot drum mixer handles about 2 sixty-pound bags per batch — 190 bags means roughly 95 batches. At 10–15 minutes per batch to load, mix, wheel, and place, that’s 16–24 hours of continuous mixing before screeding and finishing even start. Nobody mixes 190 bags by hand in one day — this paragraph is really an argument for the truck.
After the pour, protect your work. Concrete is walkable in 24–48 hours, ready for light use in about 7 days, and reaches full design strength around 28 days. Keep it damp for the first few days (a light misting or wet curing cover) and keep vehicles off a new slab for at least a week. Saw-cut control joints within 24 hours — typically one joint every 8–10 feet — to give shrinkage cracks somewhere to go.
How we calculate
Volume uses the rectangular-prism formula (length × width × depth), converted at 27 ft³ per cubic yard. Bag counts divide volume by 0.45 ft³ per 60-lb bag — the yield printed on most US concrete-mix bags; always confirm against your product label. The 10% waste allowance covers uneven excavation, spillage, and minor measurement differences; it is a planning figure, not an engineering specification. Assumes uniform slab thickness over a level, compacted subgrade.
Reviewed September 2026 · TrueMeasure
Frequently asked questions
How many 60-lb bags of concrete do I need for a 16×16 slab?
190 bags at 4 inches thick before waste — 209 with a 10% allowance.
How thick should a 16×16 slab be?
Four inches is standard for patios, walkways, and shed floors; driveways and heavier loads usually call for 5–6 inches. Frost depth, soil conditions, and local code can change the requirement — check before you form up.
Should I order ready-mix or mix bags for a 16×16 slab?
At 3.16 cubic yards, ready-mix. At 190 bags (5.7 tons), bags cost more per yard and the pour would take days.
How much does a 16×16 concrete slab cost?
Materials only, budget roughly $840–$1,250 for bags (209 × typical $4–$6 per sixty-pound bag) or a per-yard ready-mix quote plus delivery. Forming lumber, gravel sub-base, reinforcement, and labor are on top. Prices vary widely by region — get local quotes.