Mulch Calculator
By Concrete Knowhow Editorial Team · Updated April 2024 · 4 min read
Quick Answer
Enter your bed's length, width, and desired depth to instantly get cubic feet, cubic yards, and how many 2 ft³ or 3 ft³ bags of mulch you need.
Length
Width
Depth
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Round up to cover odd-shaped beds and avoid a second trip to the store.
Enter dimensions above to see results
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Common Bed Sizes — Quick Reference
| Bed Size | Depth | Cubic Yards | 2 ft³ Bags | 3 ft³ Bags |
|---|---|---|---|---|
| 10×10 ft | 2" | 0.62 | 9 | 7 |
| 10×10 ft | 3" | 0.93 | 13 | 9 |
| 10×20 ft | 2" | 1.23 | 17 | 12 |
| 10×20 ft | 3" | 1.85 | 25 | 17 |
| 20×20 ft | 3" | 3.70 | 50 | 34 |
| 20×40 ft | 3" | 7.41 | 100 | 67 |
| 50×50 ft | 2" | 15.43 | 209 | 139 |
No waste buffer included. Add 5–10% for irregular shapes.
How to Mulch a Garden Bed — Step by Step
- Weed thoroughly. Pull all weeds before mulching. Mulch suppresses future weed seeds but won't kill established weeds already in the bed.
- Edge the bed. Cut a clean edge with a spade or edging tool to define the border and keep mulch from spreading onto the lawn.
- Water the soil. If the ground is dry, water it before mulching. Mulch locks in whatever moisture is present — start with moist soil.
- Apply a pre-emergent (optional). For beds prone to weed pressure, apply a granular pre-emergent before laying mulch, following label directions.
- Spread mulch 2–4 inches deep. Pour mulch into the bed and rake it level. Aim for a consistent 3-inch depth for most situations.
- Keep mulch away from stems and trunks. Leave a 2–3 inch gap around plant bases and tree trunks. Mulch piled against stems traps moisture and promotes rot and disease.
- Fluff the edges. Use a rake to feather the mulch at bed edges so it doesn't mound up against edging or lawn borders.
- Top up annually. Check depth each spring. Add a fresh 1–2 inch layer as needed rather than replacing the entire bed.
Frequently Asked Questions
- How much mulch do I need for a 10×20 ft bed at 3 inches deep?
- A 10×20 ft bed at 3 inches deep is 50 cubic feet, or about 1.85 cubic yards. That equals 25 bags of 2 ft³ mulch or 17 bags of 3 ft³ mulch.
- How deep should mulch be?
- Apply mulch 2–4 inches deep for most landscape beds. Shredded wood mulch at 3 inches is the most common recommendation — deep enough to suppress weeds and retain moisture, but not so deep it smothers plant roots. Keep mulch 2–3 inches away from plant stems and tree trunks.
- How many bags of mulch are in a cubic yard?
- One cubic yard equals 27 cubic feet. A 2 ft³ bag gives you 13.5 bags per cubic yard; a 3 ft³ bag gives you 9 bags per cubic yard. Bulk mulch by the yard is almost always cheaper for areas over 3 cubic yards.
- How often should I replace mulch?
- Top up mulch every 1–2 years. Organic mulches like shredded bark and wood chips decompose and enrich the soil over time. Check depth in spring — if it has fallen below 2 inches, add a fresh layer rather than replacing everything.
- What type of mulch is best?
- Shredded hardwood bark is the most versatile — it stays in place, decomposes slowly, and looks tidy. Pine straw works well around acid-loving plants. Cedar and cypress resist insects and decompose more slowly. Avoid dyed rubber mulch near edible plants.
- Should I remove old mulch before adding new?
- Usually no. If the existing layer is still 1–2 inches deep and not matted, just loosen it with a rake and add a fresh top layer. Remove and replace only if the old mulch has become a thick, matted layer over 4–5 inches or shows signs of fungal growth.