Compost calculator
Enter the area and how thick you want the compost layer. You get the volume and the bags you need from their size in litres or cubic feet.
Purchase quantity
1.962 yd³
Net measurement: 1.962 yd³
- Bags of compost30 bag
- Bulk compost1.962 yd³
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How it's calculated (visible formula)
volume = area × depth; bags = ceil(volume ÷ bag size)
- Net geometric measurement, no waste.
- Adjustable waste % for cuts and breakage.
- Purchase rounded up to sellable units (boxes, bags, buckets, boards).
How to calculate it, step by step
- Measure the area of the beds or lawn.
- Pick a depth: ½–1 in as a yearly top-up or 2–3 in for a new bed.
- Multiply area by depth for the volume.
- Convert to the bag unit (cubic feet or litres) and divide.
- Above 2–3 yd³, compare against bulk pricing.
Worked example: 320 sq ft garden at 2 in
- 320 sq ft × 2 in ≈ 2 yd³ (1.5 m³)
- ≈ 53 cu ft
- 53 ÷ 1.5 cu ft bags ≈ 36
→ About 36 bags of 1.5 cu ft, or 2 yd³ in bulk.
Common mistakes
- Piling on more than 2–3 in at once: better in yearly layers.
- Buying by weight when the bag states volume.
- Not mixing it into the soil in new raised beds.
Pro tips
- Mix compost into the top 6–8 in of soil in new beds.
- Use screened compost for lawn top-dressing — coarse material smothers grass.
- Don't apply unfinished compost against sensitive roots.
- Apply in fall or late winter so it settles in before planting.
From calculation to quote
Add labour, overhead and your margin, and generate the professional PDF.
FAQs
- How thick should compost be?
- ½–1 in as a yearly top-up; 2–3 in when preparing a new bed.
- How many cubic feet in a cubic yard?
- 27 cubic feet.
- Can I top-dress a lawn?
- Yes: ¼–½ in of screened compost after aerating.
- How much compost per square foot?
- About 0.1–0.25 cu ft per sq ft for a 1–3 in layer.
- Compost or manure?
- Compost is more stable; manure must be well aged to avoid burning plants.
- How much does a bag of compost weigh?
- A 1 cu ft bag weighs about 25–40 lb depending on moisture.
Sources and standards
Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.