Landscape and building materials get sold in three unrelated unit families: volume (cubic yards, cubic feet), packages (bags of a stated size or weight), and weight (tons). Your project is measured in a fourth — square feet and inches of depth. This page is the bridge between all four.
The two identities that generate everything
1 cubic yard = 27 cubic feet
1 cubic yard covers 324 ft² at 1 inch deepThe second follows from the first: 27 ft³ × 12 inches per foot = 324 square-foot- inches per cubic yard. Every table below is one of those two numbers divided by something, which is worth knowing because it means you can always rebuild the answer from scratch:
cubic yards = area (ft²) × depth (in) ÷ 324
cubic feet = cubic yards × 27
bags = cubic feet ÷ bag size (ft³)
tons = cubic yards × density (tons per yd³)Cubic yards to cubic feet
| Cubic yards | Cubic feet |
|---|---|
| 0.25 | 6.75 |
| 0.5 | 13.5 |
| 0.75 | 20.25 |
| 1 | 27 |
| 1.5 | 40.5 |
| 2 | 54 |
| 3 | 81 |
| 5 | 135 |
| 10 | 270 |
Going the other way, divide by 27: 100 cubic feet is 3.7 cubic yards.
Cubic yards to bags
Bags sold by volume — mulch, most soil amendments, some stone — convert directly: 27 ÷ bag size.
| Bag size | Bags per cubic yard | Round up to |
|---|---|---|
| 0.5 ft³ | 54 | 54 |
| 0.75 ft³ (a typical 40 lb topsoil bag) | 36 | 36 |
| 1 ft³ | 27 | 27 |
| 1.5 ft³ | 18 | 18 |
| 2 ft³ | 13.5 | 14 |
| 2.5 ft³ | 10.8 | 11 |
| 3 ft³ | 9 | 9 |
Bags sold by weight with a stated yield — concrete and mortar mixes — use the yield printed on the bag:
| Concrete bag | Yield | Bags per cubic yard |
|---|---|---|
| 40 lb | 0.30 ft³ | 90 |
| 60 lb | 0.45 ft³ | 60 |
| 80 lb | 0.60 ft³ | 45 |
Those yields hold for standard mixes; fast-setting and specialty products yield differently. The concrete guide works through a full slab.
Area, depth, and cubic yards
Coverage halves every time depth doubles:
| Depth | 1 cubic yard covers | Cubic yards per 100 ft² |
|---|---|---|
| 1 in | 324 ft² | 0.31 |
| 2 in | 162 ft² | 0.62 |
| 3 in | 108 ft² | 0.93 |
| 4 in | 81 ft² | 1.23 |
| 5 in | 65 ft² | 1.54 |
| 6 in | 54 ft² | 1.85 |
Cubic yards to tons
Weight per unit volume is density, and it varies with the material, its gradation, and how wet it is. Treat these as typical planning values, not constants — a quarry can quote its own and be right:
| Material | Tons per yd³ | Cubic yards per ton | lb per ft³ |
|---|---|---|---|
| Bark mulch (dry) | 0.2–0.4 | 2.5–5.0 | 15–30 |
| Large rock (2–6 in) | 1.25 | 0.80 | 93 |
| Pea gravel (⅜ in) | 1.35 | 0.74 | 100 |
| Crushed stone / #57 | 1.4 | 0.71 | 104 |
| Sand (dry) | 1.4 | 0.71 | 104 |
| Crushed gravel (¼–2 in) | 1.5 | 0.67 | 111 |
| Crusher run / road base | 1.5–1.6 | 0.63–0.67 | 111–119 |
| Crushed limestone (dense) | 1.6–1.7 | 0.59–0.63 | 119–126 |
The lb-per-cubic-foot column is just tons per yd³ × 2,000 ÷ 27, and it’s the
column to use when you’re deciding whether something fits in your truck.
When you don’t know what you’re getting, 1.4 is the safe default for crushed stone. Calculators that use 1.5 for everything over-order about 7% on typical sub-2-inch material.
Tons, pounds, and the weight-versus-volume trap
A US short ton is 2,000 lb. (A metric tonne is 2,205 lb — rare in US aggregate pricing, but worth confirming on imported spec sheets.)
The trap is that some bags state volume and others state weight, and they do not convert the same way:
- A 2 cu ft bag of mulch is a volume. 13.5 make a cubic yard.
- A 40 lb bag of topsoil is a weight. Its volume is roughly 0.75 ft³ — so it takes about 36 to make a cubic yard, nearly three times as many. And that 0.75 ft³ shrinks as the soil gets wetter, because you’re buying the water.
Compare prices only after both are in dollars per cubic foot. This single conversion error is why bagged topsoil so often looks cheaper than it is, and it drives the whole bagged vs bulk cost comparison.
One more unit trap: when a supplier says “a yard,” they mean a cubic yard. A square yard is 9 ft² and has nothing to do with it.
One area, three answers
Take 200 ft² at 3 inches deep and run it through every unit:
Volume: 200 × 3 ÷ 324 = 1.85 cubic yards
1.85 × 27 = 50 cubic feet
As mulch, 2 cu ft bags: 50 ÷ 2 = 25 bags
As mulch, 3 cu ft bags: 50 ÷ 3 = 16.7 → 17 bags
As gravel (#57, 1.4): 1.85 × 1.4 = 2.59 tons
plus 10% compaction: 2.59 × 1.1 = 2.85 → order 3.0 tonsSame hole in the ground, four different order forms. Notice that the gravel gets a compaction allowance and the mulch doesn’t — mulch is loose fill with no cut waste and nothing compacts it, so the calculated number is the number you buy.
Quick lookup: any bed at 3 inches
| Area | Cubic yards | 2 cu ft bags | 3 cu ft bags | Tons (1.4, +10%) |
|---|---|---|---|---|
| 50 ft² | 0.46 | 7 | 5 | 1.0 |
| 100 ft² | 0.93 | 13 | 9 | 1.5 |
| 150 ft² | 1.39 | 19 | 13 | 2.5 |
| 200 ft² | 1.85 | 25 | 17 | 3.0 |
| 300 ft² | 2.78 | 38 | 25 | 4.5 |
| 400 ft² | 3.70 | 50 | 34 | 6.0 |
| 500 ft² | 4.63 | 63 | 42 | 7.5 |
| 750 ft² | 6.94 | 94 | 63 | 11.0 |
| 1,000 ft² | 9.26 | 125 | 84 | 14.5 |
For 4-inch depth, multiply the 3-inch row by 1.33; for 2 inches, multiply by 0.67.
Rounding rules by material
Rounding is not a rounding error — it’s how the supplier bills you.
| Material | Sold in | Round |
|---|---|---|
| Bagged anything | Whole bags | Up, always |
| Bulk mulch and soil | Half or whole cubic yards | Up to the next half yard |
| Gravel and aggregate | Half tons, often with a delivery minimum | Up to the next half ton |
| Ready-mix concrete | Quarter or half yards, ~1 yard minimum | Up, plus a waste factor |
Round up for a simple asymmetry: leftover mulch mulches something else, while running short means another trip, another delivery fee, or in the case of concrete, a cold joint in your slab.
Add a waste factor only where the material is cut, spilled, or compacted: about 10% for concrete, 10–20% for compacted gravel base, 5–10% for loose-laid decorative stone, and none for mulch.
The five conversion mistakes
1. The ”× 0.0031” shortcut. 1 ÷ 324 = 0.0030864, and people round it to 0.0031. On our 200 ft² example that gives 1.86 instead of 1.8519 cubic yards — which crosses a bag boundary and tells you to buy 26 bags instead of 25. Divide by 324; don’t multiply by a rounded decimal.
2. Forgetting to convert depth. Depth is in inches, area in feet. Either divide inches by 12 to get feet, or use the ÷ 324 identity, which already has the conversion baked in. Doing neither produces answers 12× too large.
3. Using one density for every stone. The spread from large rock (1.25) to dense limestone (1.7) is 36%. On a 20-ton order that’s the difference between one truck and two.
4. Ordering yards and being billed tons (or the reverse). Say the unit out loud when you order, and ask what density they converted at.
5. Applying a compaction allowance to the wrong material. Compacted base layers need 10–20%. Loose mulch needs none. Adding one to the other is how you end up with a pile that never goes away.
Metric conversions
| From | To | Multiply by |
|---|---|---|
| Cubic yards | Cubic metres | 0.765 |
| Cubic metres | Cubic yards | 1.308 |
| Cubic feet | Cubic metres | 0.0283 |
| Square feet | Square metres | 0.0929 |
| Inches | Millimetres | 25.4 |
| US short tons | Tonnes | 0.907 |
| Tonnes | US short tons | 1.102 |
Frequently asked questions
How many cubic feet are in a yard of mulch? 27 — the same as a cubic yard of anything else. Volume doesn’t care what’s in it.
How many tons is a cubic yard of gravel? About 1.4 for typical crushed stone, so one ton is about 0.71 cubic yards. Pea gravel runs a little lighter, crusher run and dense limestone heavier.
How many bags of mulch are in a cubic yard? 13.5 of the 2 cu ft size (buy 14) or 9 of the 3 cu ft size. The mulch guide covers depth and coverage in full.
How do I convert square feet to cubic yards? You can’t without a depth. Multiply square feet by depth in inches, then divide by 324.
How many 40 lb bags of topsoil make a cubic yard? About 36, because a 40 lb bag is roughly 0.75 ft³ — but weight-labeled bags vary with moisture, so read the cubic feet on the bag if it’s printed.
Why is gravel priced by the ton but measured in yards? Trucks and scales work in weight, projects work in volume. Density is the conversion, which is why the gravel guide makes you pick a stone type before it gives you a number.
Does paint work the same way? No — paint is sold by the gallon against area coverage, not volume, so there’s no cubic-yard step at all. See how much paint you need.
Put these conversions to work in the Mulch Calculator or the Gravel Calculator, or read the rest of the material guides.