Step 1 — Measure your beds (all of them)
Walk the yard with a tape. For each bed: length × width in feet. Round generous — mulch is forgiving, and leftover bags stack; running out mid-job isn't forgiving at all.
- Rectangles: length × width. L-shaped bed? Split it into two rectangles and add.
- Circles: measure across the widest point (diameter), area = π × (d÷2)². A 10 ft circle ≈ 79 ft².
- Borders along a house: average width × length. A 3 ft border along a 40 ft wall = 120 ft².
- Trees: measure out to the drip line (branch tips), not the trunk — that's the mulch ring that matters.
Step 2 — Choose your depth
| Situation | Depth |
|---|---|
| Refreshing existing mulch | 1–2 in |
| Standard beds, most flowers & shrubs | 2–3 in |
| New bed over bare/weedy soil | 3–4 in |
| Paths & utility strips | 3–4 in |
University extensions ( Clemson, Iowa State, and others) consistently recommend 2–4 inches after settling. More than 4 inches around plants traps moisture and blocks air; less than 2 lets weeds through.
Step 3 — Convert to yards or bags
total ft³ = area × depth ÷ 12 → yd³ = ft³ ÷ 27 → bags = ft³ ÷ bag size
Worked example — typical front yard: two 20×4 ft foundation borders (160 ft²) + one 10 ft circle bed (79 ft²) = 239 ft². At 3 inches: 239 × 3/12 = 59.7 ft³ = 2.2 yd³. With 10% settling: order 2.5 yards bulk, or 33 of the 2 ft³ bags.
The two classic mistakes
- Forgetting compaction. Fresh-blown or loose mulch settles 10–20% in the first month. The fix is built into our calculator's “+10%” switch.
- Misjudging depth on refreshes. Rake the old mulch before measuring — if you already have 2 inches down, you're topping up 1 inch, not 3.
Run your own numbers in the mulch calculator, or grab the pre-computed numbers in our mulch coverage chart.