Peat Moss Calculator
Enter your bed or planting area and the mix-in depth to get the cubic yards, weight, and bag count of peat moss you’ll need.
Measure straight across the widest point.
Adjust depth below if needed.
Covers spillage and compaction. 5–10% is normal.
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Bags or bulk delivery?
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Coverage & weight
Material profile
For the default 15 ft × 10 ft bed amended 2 inches deep, you’ll need about 1.02 cubic yards (0.41 tons) of standard sphagnum peat moss, including 10% waste. Round up to 0.5 tons for bulk ordering — roughly $148.33 delivered, versus $896 in 0.5 cu ft bags.
Peat moss needed for common project sizes
These estimates use standard sphagnum peat moss at 800 lb per cubic yard with a 10% waste allowance built in.
| Project | Depth | Cubic yards | Tons |
|---|---|---|---|
| Small soil amendment, 50 sq ft | 2 in | 0.34 yd³ | 0.14 tons |
| Medium soil amendment, 200 sq ft | 2 in | 1.36 yd³ | 0.54 tons |
| New garden bed, 100 sq ft | 4 in | 1.36 yd³ | 0.54 tons |
| Large new bed, 300 sq ft | 4 in | 4.07 yd³ | 1.63 tons |
| Potting mix component, 50 sq ft | 1 in | 0.17 yd³ | 0.07 tons |
| Large soil amendment, 500 sq ft | 2 in | 3.4 yd³ | 1.36 tons |
Peat moss grades, weight and best use
| Type | Weight per yd³ | Best for | Drainage |
|---|---|---|---|
| Standard sphagnum peat moss | 800 lb | Soil amendment, acid-loving plants | Good, high water retention |
| Fine-grade peat moss | 850 lb | Seed starting mixes | Good |
Figures are for dry material. Wet or freshly delivered material can weigh noticeably more.
How to calculate peat moss you need
- Measure the planting area length × width in feet for a bed, or use the circle/border option for pots and rings.
- Set the mix-in depth 1in for potting mixes, 2in for general soil amending, 4in for building a new acid-loving bed.
- Pick a grade standard peat for general garden use, fine-grade for seed-starting and potting mixes.
- Add waste 10% covers compression loss and spillage — peat moss expands significantly once loosened from a compressed bale.
- Compare bale/bag vs. bulk pricing compressed bales are the standard retail unit; bulk loose peat is rare and mainly for large nurseries.
Worked example
Using the calculator’s default 15 ft × 10 ft bed amended 2 inches deep with standard peat moss:
- Area15 ft × 10 ft = 150 sq ft
- Depth in feet2 in ÷ 12 = 0.167 ft
- Volume150 sq ft × 0.167 ft = 25.0 cu ft
- Plus 10% waste25.0 × 1.10 = 27.5 cu ft
- Cubic yards27.5 ÷ 27 = 1.02 yd³
- Weight (standard peat moss, 800 lb/yd³)1.02 × 800 = 814.8 lb = 0.407 tons
- Order amountRound up to 0.5 tons — order in half-ton or bale-count increments
- Bagged option27.5 cu ft ÷ 0.5 cu ft/bag = 56 bags × $16 = $896, versus $148.33 for bulk plus delivery
Recommended depth by project
| Project | Recommended depth | Notes |
|---|---|---|
| Potting mix component | 1 in | Blended into potting soil for moisture retention, roughly 1/3 by volume |
| Soil amendment mix-in | 2 in | Tilled into existing beds to improve water retention and lower pH slightly |
| New garden bed | 4 in | Worked into the full bed depth when establishing acid-loving plantings |
| Seed-starting trays | Thin layer, blended | Fine-grade peat mixed with perlite/vermiculite for germination mix |
| Blueberry/azalea beds | 4-6 in | Heavier application for acid-loving shrubs that need sustained moisture |
Bags or bulk delivery?
Peat moss is almost always sold in compressed bales (commonly 2 or 3 cu ft compressed, expanding once opened) rather than loose bulk, so bagged pricing is the norm for most homeowners. True bulk loose peat is mainly available to nurseries and large landscaping operations and only pays off on big jobs.
- Small beds/potsunder about 0.5 ton (roughly 25-30 compressed bales) — bales are the only practical option.
- Medium gardens0.5 to 1.5 tons — compare bale totals against any bulk quote your supplier offers.
- Large nursery/farm jobsover 1.5 tons — ask suppliers about bulk loose peat, which cuts the per-cubic-yard cost significantly.
Common mistakes
- Not pre-wetting dry peat mossdry peat moss is extremely hydrophobic and can take repeated watering to fully absorb moisture; wet it thoroughly before mixing it in.
- Using peat moss alone as a growing mediumpeat has almost no nutrients on its own; blend it with compost or fertilizer, not as a stand-alone soil.
- Ignoring the pH droppeat moss is acidic and lowers soil pH over time — great for blueberries and azaleas, but can hurt plants that prefer neutral or alkaline soil if overused.
- Forgetting it compresses in the balea compressed bale expands significantly once opened and fluffed — buying by compressed volume alone under-estimates usable volume, which this calculator’s waste factor helps offset.
- Not considering peat-free alternativescoir (coconut fiber) is a common substitute with similar water retention and a smaller environmental footprint, worth considering for sustainability-conscious projects.
- Using fine-grade peat for structural bed amendingfine-grade peat is meant for seed-starting and potting mixes; standard grade holds structure better in garden beds.
What this calculator assumes
Adjust your result if your project differs from these.
- Depth is the amount mixed in or applied, measured after the peat is fluffed and loosened from its compressed bale.
- Default grade is standard sphagnum peat moss at roughly 800 lb per cubic yard once loosened.
- 10% waste accounts for compression variance and spillage during mixing.
- Prices are material only — tilling and mixing labor are separate.
- Peat moss is assumed dry-to-moist as purchased; pre-wetting changes weight but not the ordered volume.
- Bag size is 0.5 cu ft loosened volume, a common reference size for peat moss bales.
Common questions
How much peat moss do I need per square foot?
For a standard 2-inch mix-in, figure about 0.17 cubic feet per sq ft before waste — or use the calculator above with your exact bed size.
What's the difference between peat moss and compost?
Peat moss improves water retention and lowers pH but has almost no nutrients; compost adds organic matter and nutrients. Most beds benefit from a blend of both.
How much does a compressed bale of peat moss cover?
A typical 2 cu ft compressed bale expands to roughly 3-4 loosened cubic feet, covering about 18-24 sq ft at 2 inches deep.
Does peat moss lower soil pH?
Yes, peat moss is naturally acidic (pH 3.5-4.5), which makes it useful for acid-loving plants like blueberries and azaleas but something to watch for pH-sensitive crops.
Is peat moss good for vegetable gardens?
In moderation, yes — it improves water retention in sandy soil, but blend it with compost since it has no nutritional value on its own.
How deep should peat moss be for a new garden bed?
4 inches worked into the full bed depth is typical when establishing a new acid-loving planting area.
Is coco coir a better alternative to peat moss?
Coir is a more renewable substitute with similar water retention, though it’s pH-neutral rather than acidic, so it won’t lower soil pH the way peat does.
How much does peat moss cost for a small bed?
For the calculator’s default 150 sq ft bed at 2 inches, expect about $896 in bags versus $148.33 if you can source bulk loose peat with delivery.
Why won't my peat moss absorb water?
Dry peat is hydrophobic — water beads and runs off instead of soaking in. Pre-wet it in a bucket or wheelbarrow before spreading, or water it slowly and repeatedly once placed.
Can I use peat moss for potting mix?
Yes, fine-grade peat moss is a standard component of potting and seed-starting mixes, typically blended with perlite or vermiculite for drainage.
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Project
| Shape | — |
| Dimensions | — |
| Depth | — |
| Area | — |
| Material | — |
| Waste allowance | — |
Volume & weight (incl. waste)
| Cubic yards | — |
| Cubic feet | — |
| Weight | — |
| Tons (rounded up) | — |
Shopping list
| Bulk order | — |
| Bagged alternative (0.5 cu ft) | — |
| Estimated cost | — |
Notes
Estimate generated by materialcalculate.com. Assumes uniform depth and standard dry material densities. Confirm quantities with your supplier before ordering.