Compost Calculator — Top-Dressing and Bed Prep
Set your conditions — the recommendation updates instantly.
GardenSays
You need about 2.7 cu ft of compost (top-dressing) — that's 3 bags (1 cu ft) or 0.1 cubic yards in bulk.
- Volume
- 2.7 cu ft
- Bulk
- 0.1 cu yd
- Bags
- 3 × 1 cu ft
A 8×4 ft area at 1 inches deep works out to 2.7 cubic feet. At under a cubic yard, bags are the practical choice: 3 × 1 cu ft bags.
For established beds, a 1-2 inch layer of compost worked into the top few inches each season maintains organic matter.
Why
- ✓Buying by volume (not guessing by weight) is the only reliable way to fill a bed — moisture makes weight wildly inconsistent.
- ✓Below one cubic yard, delivery fees usually erase the bulk discount.
When this doesn't apply
- →Material settles: expect a raised bed fill to drop 10-20% in the first season; buy a little extra or top up later.
- →Irregular or L-shaped areas: split into rectangles, run each through the calculator, and add the results.
How this was calculated
- 1. Area32 sq ft
8 ft × 4 ft
- 2. Volume2.7 cu ft
32 sq ft × 1/12 ft deep
- 3. In cubic yards0.1 cu yd
2.7 cu ft ÷ 27 (bulk delivery is sold by the yard)
- 4. In bags3 bags
2.7 cu ft ÷ 1 cu ft per bag, rounded up
Data sources
- University of Minnesota Extension — Composting in home gardens (checked 2026-07-15)
Community choice
Anonymous, one tap. What did you do?
People also ask
- How much compost should I add to my garden? →
- What is the compost to soil ratio for raised beds?
- How much soil for a raised bed? →
Your next decisions
More soil, mulch & compost tools: see all →