Compost Calculator — Volume for Gardens, Beds & Top Dressing

Calculator

Length

Width

Depth

Soil type

Bulk price (per yd³)

$/yd³

Bag price (1 ft³)

$/bag

You need

3.70 cubic yards

= 100.00 ft³ · 4.81 tons · ≈ 100 bags (1 ft³)

Bulk: $111 · Bagged: $400 (save $289 with bulk)

How to Calculate Compost Quantity

Compost calculation uses the same volume math as any bulk material — area times depth gives cubic feet, divided by 27 gives cubic yards. The unique consideration with compost is that you almost never use it pure; it's a soil amendment that gets mixed into existing soil rather than used as a base material.

Cubic yards = (Area in sq ft × Depth in inches) ÷ 324
Weight (tons) = Cubic yards × 1.10 (compost density)
Mix ratio = 25-30% compost to 70-75% topsoil for planting beds

Compost density of 1.10 t/yd³ assumes finished, properly aged compost. Fresh or partially decomposed compost has higher moisture content and weighs more. For ordering purposes, use the dry density; for trucking weight calculations, add 15-20% for actual delivery weight.

Worked example: amending a vegetable garden

Existing 200 sq ft vegetable garden bed, applying 2 inches of compost to till in for the new growing season:

Volume: (200 × 2) ÷ 324 = 1.23 cubic yards
In cubic feet: 33 ft³
Weight: 1.23 × 1.10 = 1.36 tons (2,720 lb)
Bulk cost (at $35/yd³): 1.23 × $35 = $43
Bagged (33 bags of 1 ft³ at $5): $165
Savings with bulk: $122

Never plant in pure compost

Compost is concentrated nutrients and organic matter — too rich for direct planting. Pure compost beds become waterlogged, over-fertilize plants (causing leaf burn), and compact into a dense mat over time. Always blend compost with mineral soil at 25-30% maximum for planting, or use as a 1-2 inch top dressing on existing soil.

How Much Compost by Project Type

Different garden applications need different compost amounts. The biggest mistake gardeners make is over-applying — more compost isn't better past a certain point.

New vegetable garden bed (in-ground)

Apply 2-3 inches of compost over the area, then till into top 8 inches of existing soil. For 100 sq ft bed at 3 inches: 0.93 cubic yards (1 ton). For 200 sq ft: 1.85 yd³. The till-in is critical — pure compost layered on top doesn't penetrate where roots need it.

Annual top-dressing existing garden

1 inch of compost per year maintains soil organic matter for established beds. For 200 sq ft: 0.62 cubic yards (0.68 tons) annually. Apply in fall after final harvest for maximum integration before spring planting.

Raised bed mix (initial fill)

Blend 30% compost with 60% topsoil and 10% peat moss or aged manure. For a 4x8 raised bed at 12 inches deep (1.19 yd³ total): 0.36 cubic yards (0.40 tons) of compost. For a 4x4 bed: 0.18 yd³.

Raised bed annual refresh

Add 2 inches of fresh compost to the top of established raised beds each season: 0.20 cubic yards per 4x8 bed. Mix into the top 4 inches with a hand fork before spring planting.

Lawn top-dressing

Apply 1/4 inch of screened compost over established lawn — this is the maximum without smothering grass. For 1,000 sq ft of lawn: 0.77 cubic yards (0.85 tons). Rake in evenly and water thoroughly. Best done after core aeration in fall.

Tree and shrub planting

Mix 1 part compost with 2 parts native soil from the planting hole. For a typical small tree planting hole (3 ft diameter × 2 ft deep): about 0.5 ft³ of compost per tree. Don't over-amend — trees that root only in amended soil never extend roots properly into native soil.

Compost Coverage Table

How many square feet 1 cubic yard or 1 ton of compost covers at common depths:

Depth	Per cubic yard	Per ton	Per 1 ft³ bag
1/4 inch (top dressing)	1,296 sq ft	1,178 sq ft	48 sq ft
1/2 inch	648 sq ft	589 sq ft	24 sq ft
1 inch (annual refresh)	324 sq ft	295 sq ft	12 sq ft
2 inches (light amendment)	162 sq ft	147 sq ft	6 sq ft
3 inches (new bed amendment)	108 sq ft	98 sq ft	4 sq ft
6 inches (heavy renovation)	54 sq ft	49 sq ft	2 sq ft

Types of Compost

"Compost" covers a range of materials. Different types serve different purposes — and quality varies enormously even within categories.

Yard waste compost

Made from leaves, grass clippings, branch chippings. The most common municipal compost. Free or very cheap ($15-30/yd³). Quality varies — some municipal compost is excellent, others contain weed seeds or contamination. Inspect before bulk delivery.

Food waste compost

Made from kitchen scraps, food processing waste. Higher nitrogen than yard waste compost. Often available from commercial composting operations. Cost: $30-50/yd³.

Manure compost

Aged animal manure (cow, horse, chicken, etc.) blended with bedding material and composted. Excellent for vegetable gardens — slow-release nutrients. Must be properly aged (6+ months) before use. Cost: $25-55/yd³. Free if you have local livestock connections.

Mushroom compost

Byproduct of commercial mushroom growing. High in calcium and slightly alkaline (pH 6.5-7.5). Excellent for tomatoes, peppers, and vegetables that prefer alkaline soil. Cost: $30-55/yd³. Regional availability — common in mushroom-growing states.

Vermicompost (worm castings)

Composted by red worms. The premium soil amendment — extremely concentrated nutrients. Apply sparingly: 1/4 to 1/2 inch is plenty. Cost: $4-8 per gallon (or $250-500/yd³). Mostly sold in small quantities for high-value plants.

Biodynamic / organic certified compost

Premium compost made under specific organic standards (USDA Organic, biodynamic certification). Cost: $50-90/yd³. Worth the premium for certified organic farms and discerning gardeners.

Compost Pricing in 2026

Compost type	Per yard (bulk)	Per 1 ft³ bag	Per 1.5 ft³ bag
Yard waste (municipal)	$15–30	$3–5	$4–7
Mixed food/yard waste	$25–45	$4–6	$5–8
Aged manure	$25–55	$5–8	$6–10
Mushroom compost	$30–55	$5–7	$6–10
Vermicompost (worm castings)	$250+	$15–25	—
Premium / organic certified	$50–90	$7–12	$10–15

Check your local municipality — many cities offer free yard waste compost from autumn leaf collection. The quality is often excellent if you can pick it up yourself. Delivery typically adds $50-150 for paid bulk orders.

Application Timing

When you apply compost matters as much as how much you apply:

Fall (best for vegetable beds): October-November application gives compost 4-6 months to integrate before spring planting. Earthworms and freeze-thaw cycles do the mixing for you.
Early spring (acceptable): Apply 2-4 weeks before planting to let nutrients stabilize. Till in immediately rather than letting it sit on the surface.
After lawn aeration (fall): The single best time to top-dress a lawn. Cores left by aeration give compost direct soil contact.
Mid-summer (avoid for new applications): High temperatures accelerate nitrogen loss. Stick to annual top-dressing only during summer months.
Winter (skip): Frozen ground prevents integration. Stockpile compost for spring application instead.

Making Your Own Compost

For small gardens, home composting can supply some or all of your compost needs at minimal cost:

Yield: A standard 3x3x3 ft compost bin produces 3-5 cubic feet of finished compost annually.
Time: 6-12 months from start to finished compost (faster with active management, slower for passive piles).
Ratio: 3 parts "browns" (dry leaves, straw, paper) to 1 part "greens" (kitchen scraps, grass clippings).
Cost: $0 if you have yard waste and kitchen scraps. Compost bins range $30-200.
Limitation: Home composting is great for small gardens but rarely produces enough for major projects. For raised beds or new lawn install, supplement with bulk delivery.

Common Compost Mistakes

Planting in pure compost: Waterlogged roots, over-fertilized plants. Always mix with mineral soil at 25-30% max.
Using unfinished compost: Partially decomposed compost ties up nitrogen as it finishes — plants turn yellow. Wait for compost to be dark, crumbly, and odorless.
Over-applying for top dressing: 1/4 inch maximum on lawns. Thicker layers smother grass.
Buying bagged for large projects: Bagged compost at home stores is 3-5x more expensive than bulk. Bulk pays off above 0.5 cubic yards.
Skipping the till-in: Compost layered on top doesn't penetrate where roots need it. Always till into top 6-8 inches of soil.
Using fresh manure: Fresh manure burns plant roots. Always age 6+ months before garden use.

Frequently Asked Questions

How much compost do I need for my garden?

For new garden bed installation, apply 2-3 inches of compost and till into existing soil 6-8 inches deep. For a 100 sq ft bed at 3 inches: 0.93 cubic yards (~1 ton). For top dressing existing beds: 1 inch per year = 0.31 yd³ per 100 sq ft.

How much compost per square foot?

For new beds, use approximately 0.25 cubic feet of compost per square foot at 3 inches deep. For raised beds with vegetables, blend 30% compost with 60% topsoil + 10% amendments. Pure compost beds drown plants — always mix with mineral soil for proper drainage.

How much does a yard of compost weigh?

Finished compost weighs approximately 2,200 lb (1.10 tons) per cubic yard when properly aged. Fresh, partially decomposed compost can hit 2,500-2,800 lb due to higher moisture content. Compost is lighter than soil, making delivery weight limits less of a concern.

How much does compost cost?

Bulk compost runs $25-50 per cubic yard in 2026, varying by quality and location. Premium organic or biodynamic compost: $50-90/yd³. Bagged compost (1 ft³ at $4-7) is about $108-189 per yard equivalent. Many municipalities offer free compost from yard waste programs.

Can I use too much compost?

Yes. Pure compost beds become waterlogged and over-fertilize plants, causing leaf burn and excess nitrogen leaching. Apply 1-3 inches mixed into soil annually, or 1/4 inch top-dressed for established lawns. More than this provides diminishing returns and can harm plants.

How much compost for a raised bed?

For a new 4x8 ft raised bed at 12 inches deep, use 30% compost (about 0.36 cubic yards / 10 cubic feet) blended with topsoil and amendments. Pure compost beds compact and drain poorly. Annual top-up of 2 inches: 0.20 cubic yards per refresh.

How long does compost take to break down in soil?

Finished compost integrates into soil within 4-12 weeks once mixed in. Partially decomposed compost takes 6-12 months and can temporarily lock up nitrogen as it finishes. Always use finished, dark, crumbly compost for direct planting — let unfinished compost age in a pile first.

What's the difference between compost and topsoil?

Compost is decomposed organic matter — primarily a soil amendment to add nutrients and improve structure. Topsoil is mineral soil with some organic content — the base for plant growth. Use topsoil as the bulk material and compost as the amendment (typically 70-30 split or similar).

How much area does a yard of compost cover?

One cubic yard of compost covers approximately 100 sq ft at 3 inches deep, 150 sq ft at 2 inches, 200 sq ft at 1.5 inches, or 1,300 sq ft at 1/4 inch (top dressing for lawns). The lighter density compared to topsoil gives better coverage per yard.

When should I apply compost to my garden?

Fall application (October-November) gives compost 4-6 months to integrate before spring planting — ideal for vegetable beds. Spring application (April-May) works for top-dressing established beds. Avoid mid-summer applications — high temperatures accelerate nitrogen loss.

Can I make my own compost cheaper than buying?

Yes for small gardens. Home composting from kitchen and yard waste costs only your time. A 3x3 ft compost bin produces 3-5 cubic feet of finished compost per year. For projects needing more than 10 cubic feet annually, buying bulk is often more efficient than DIY production.

Is compost the same as manure?

No, though aged manure is one type of composted material. Compost is decomposed plant matter (yard waste, food scraps). Aged/composted manure adds animal manure to the mix. Fresh manure must age 6+ months before use — it's too 'hot' (high nitrogen) and can burn plants.