Mulch Calculator — Bags and Cubic Yards
Enter your bed size and how deep you want the mulch. You get a bag count, a cubic-yard figure, and a straight answer on whether bulk delivery is worth it.
About the Mulch Calculator
Mulch is the job people most often under-buy, because a thin layer looks fine on day one and then vanishes. Three inches is the working depth: enough to actually suppress weeds and hold moisture, not so much that it starts rotting stems. This works out the volume and, more usefully, tells you when you have crossed the point where bulk delivery beats hauling bags.
How to use it
- Measure the length and width of the bed in feet.
- For an irregular bed, break it into rectangles and add the results.
- Enter the depth — 3 inches for established beds, 2 inches around shallow-rooted shrubs.
- Compare the bag count against the cubic yards before you decide how to buy.
The formula
Cubic feet = length × width × (depth ÷ 12)
Bags = cubic feet ÷ bag size
Bagged mulch is normally 2 cubic feet, occasionally 3. Bulk mulch is sold by the cubic yard, which is 27 cubic feet — so one yard replaces about 13 and a half of the 2 cu ft bags.
Worked examples
| Bed | Depth | Cubic feet | 2 cu ft bags | Cubic yards |
|---|---|---|---|---|
| 20 ft × 4 ft | 3" | 20.0 | 10 | 0.74 |
| 40 ft × 5 ft | 3" | 50.0 | 25 | 1.85 |
| 100 ft × 6 ft | 3" | 150.0 | 75 | 5.56 |
| 10 ft × 10 ft | 2" | 16.7 | 9 | 0.62 |
The third row is the tipping point. Seventy-five bags is two pickup loads and an afternoon of lifting; five and a half yards is one delivery, usually for less money.
Common mistakes
- Buying by area instead of volume. Mulch is sold by volume. Two beds of identical size need completely different amounts at 2 inches versus 4.
- Going too deep against trunks. Piling mulch against a trunk — the "mulch volcano" — traps moisture and kills the tree slowly. Keep it a few inches clear of the bark.
- Forgetting mulch settles. A freshly spread 3-inch layer becomes about 2 inches within a season. Buying for the finished depth means buying short.
- Assuming all bags are 2 cubic feet. Three cubic foot bags exist and look nearly identical on the pallet. Check before you multiply.
Terms explained
- Cubic yard
- 27 cubic feet. Covers about 108 sq ft at 3 inches deep.
- Bulk mulch
- Sold loose by the yard and delivered in a dump truck. Cheaper per unit, but you need somewhere it can be tipped.
- Double-ground
- Mulch put through the grinder twice. Finer, settles faster, looks tidier.
- Weed barrier
- Fabric under the mulch. Helps for a season or two, then weeds root in the mulch on top of it anyway.
Common questions
- How many bags of mulch in a cubic yard?
- Thirteen and a half of the 2 cubic foot bags, or nine of the 3 cubic foot bags. Most people round to 14 and 9.
- How deep should mulch be?
- Three inches is the standard. Two is enough for annual beds, four starts holding too much moisture against stems.
- How much does a yard of mulch cover?
- About 108 square feet at 3 inches deep, or 162 square feet at 2 inches.
- Is bulk mulch cheaper than bags?
- Almost always past about 2 cubic yards, even after the delivery fee. Below that the fee usually cancels the saving.
- How much does a yard of mulch weigh?
- Between 400 and 800 lb depending on how wet it is. A half-ton pickup handles roughly one yard safely.
- When should I mulch?
- Late spring once the soil has warmed. Mulching too early on cold soil keeps it cold and slows everything down.
- Do I need to remove old mulch?
- Not usually. Rake it to break up any crust and top up to depth. Remove it only if it has matted into a water-repellent layer.