Solve backwards
How much ground will my compost dress?
- 16 ft³The example worked below
- Compost Blend CalculatorEvery figure is its own
You have
How much compost?
That is 16 ft³(453.1 L). Worked by the Compost Blend Calculator at the settings below.
The settings it uses
- Compost layer depth
- 2 in
- Incorporation depth
- 6 in
What it will do
96 sq ft of plot
8.92 m²
One vegetable plot. Enough for a vegetable plot about 9.8 × 9.8 ft.
Or several. Less than one vegetable plot of the size the Compost Blend Calculator opens on (a vegetable plot about 14.8 × 14.8 ft).
Check it forwards
- Area to improve
- 96 sq ft
- It asks for
- 16 ft³
- You have
- 16 ft³
The Compost Blend Calculator asks for 16 ft³ at that size.
If you had more, or less
Around your amount
Each worked by the Compost Blend Calculator at the same settings.
Half
8 ft³
48 sq ft
a vegetable plot about 6.9 × 6.9 ft
Yours
16 ft³
96 sq ft
a vegetable plot about 9.8 × 9.8 ft
Half as much again
24 ft³
144 sq ft
a vegetable plot about 12 × 12 ft
Double
32 ft³
192 sq ft
a vegetable plot about 13.9 × 13.9 ft
Common amounts
What each amount of compost covers
The sizes it is usually sold in, each worked by the Compost Blend Calculator at the settings above.
| You have | It covers | As one vegetable plot | Average vegetable plots |
|---|---|---|---|
| 8 ft³(226.5 L) | 48 sq ft(4.46 m²) | a vegetable plot about 6.9 × 6.9 ft | under 1 |
| 16 ft³(453.1 L) | 96 sq ft(8.92 m²) | a vegetable plot about 9.8 × 9.8 ft | under 1 |
| 32 ft³(906.1 L) | 192 sq ft(17.8 m²) | a vegetable plot about 13.9 × 13.9 ft | under 1 |
| 64 ft³(1,812.3 L) | 384 sq ft(35.7 m²) | a vegetable plot about 19.6 × 19.6 ft | 1 |
Depth is the number that matters
This is the reverse of most volumes on the site: the depth is small and the area large, so dressing a bed at twice the intended depth doubles the order and halves the ground covered. Twenty-five to fifty millimetres, 1 to 2 inches, is the usual annual dressing, and the calculator opens at fifty.
Dug in, it becomes a share of the soil
A 25 to 50 mm layer worked into the top 150 to 200 mm is standard soil-improvement practice. The same compost dug in deeper gives a lower concentration over more soil, and the calculator reports that share: its opening 50 mm into 150 mm is a quarter by volume, above the 5 to 10 per cent target for productive vegetable soil — it builds over seasons.
More than 75 mm at once is too much
More than about 75 mm, 3 inches, in one go can push organic content high enough to hold too much water and lock up nitrogen while it finishes breaking down. So a heap that would cover the plot twice over at 50 mm is two seasons of dressing, not one thick layer — the extra keeps.
How the answer is worked
Nothing here is a second formula. The Compost Blend Calculator runs forwards — a size in, a quantity out — and this page grows its own starting vegetable plot in proportion until the quantity it asks for is what you have. Where it rounds up to whole containers, the answer is the largest size before the next one would be needed.
Where the calculator adds an allowance for cuts or breakage when you order, the same allowance comes off here, because it is the same calculator: a stack you already own finishes less than its face value. Where it adds none, neither does this page — the settings beside the answer say which.
Compost Blend Calculator
runs it forwardsWork out how much compost to mix into an existing bed or a soil blend to reach a target organic content.
Work out what to buy insteadSolve backwards
Other things you might already have
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Bagged mulch, worked by the Mulch Calculator.
How much bed will a yard of mulch cover?
Bulk mulch, worked by the Mulch & Gravel Calculator.
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Gravel, worked by the Mulch & Gravel Calculator.
How big a bed will my topsoil fill?
Topsoil, worked by the Topsoil Calculator.
How big a raised bed will my soil fill?
Raised bed soil, worked by the Garden Soil Calculator.
How big a slab will a yard of concrete pour?
Ready-mix concrete, worked by the Concrete Calculator.
Solve backwards
Start from what is already in the yard
Paint, sheets, rolls, bags and pieces, each read the other way by the calculator that orders it.
The calculator's own figures
Nothing is estimated twice: the page runs the same calculator you would order with.
The largest size that fits
Where a calculator rounds up to whole containers, the answer stops before the next one.
Both unit systems
Gallons and litres, square feet and square metres, side by side.
Frequently asked questions
- How much plot does 16 ft³ of compost cover?
- At the Compost Blend Calculator's own settings, 96 sq ft (8.92 m²) — a vegetable plot about 9.8 × 9.8 ft. Every figure follows the settings, which you can change in the calculator.
- How much plot does 500 L of compost cover?
- At the Compost Blend Calculator's own settings, 10 m² (108 sq ft) — a vegetable plot about 3.2 × 3.2 m. Every figure follows the settings, which you can change in the calculator.
- How much area does a bag of compost cover?
- At a 50 mm (2 inch) layer, a 50 litre bag covers about 1 m² (11 square feet), and a 1.5 cubic foot bag about 9 square feet (0.8 m²). At 25 mm (1 inch) each covers twice that. Depth moves the answer far more than the bag does.
- How thick should compost be spread on a garden?
- An annual dressing of 25 to 50 mm, 1 to 2 inches, worked into the top 150 to 200 mm is standard practice. More than about 75 mm (3 inches) at once can hold too much water and lock up nitrogen while it finishes rotting, so build organic matter over several seasons.
- How much compost do I need per square metre?
- Depth in millimetres is litres per square metre, so a 50 mm dressing is 50 litres per m² and 25 mm is 25 litres. In imperial terms, a 2 inch layer is about 1 cubic foot for every 6 square feet.