Mulch Calculator — Free Online Tool
Mulch math is where gardeners either run short or end up with a mountain. This mulch calculator converts your bed dimensions and desired depth into cubic yards — and bag count for store runs.
What is the Mulch Calculator?
Three inches is the sweet spot for weed suppression without suffocating plants; new beds sometimes get four. A cubic yard covers about 100 square feet at 3 inches deep. Bagged mulch (2 cubic feet) is convenient but pricey — 13.5 bags make a yard, so bulk delivery wins for anything over a couple of yards.
Keep mulch 2–3 inches away from trunks and stems — “mulch volcanoes” against tree trunks cause rot and invite pests. Refresh annually as it decomposes; that decomposition is free soil improvement. This mulch calculator gives yards for bulk orders and bag counts for the garden center.
How to use this calculator
- Measure each bed's length and width in feet.
- Choose your depth (3" is standard).
- Click Calculate Mulch and decide bulk vs bags.
- Keep mulch pulled back 2–3" from trunks and stems.
Formula
Frequently asked questions
How deep should mulch be?
3 inches is ideal for weed control; more can suffocate roots. This mulch calculator defaults to 3.
Bulk or bagged mulch — which is cheaper?
Bulk wins beyond roughly 2 cubic yards; bags win for small touch-ups.
Can mulch touch tree trunks?
No — the 'mulch volcano' causes rot and pests. Leave a 2–3 inch gap.
How often should I refresh mulch?
Top up yearly; as it breaks down it feeds the soil — that's a feature, not a bug.