Mulch Calculator: How Much Mulch Do I Need?
Material volume planner
Estimate the amount of loose material needed for one or more spaces.
Areas
Depth and ordering details
Bulk volume and container estimates are calculated from the measurements above.
Optional cost estimate
Currency marks change the display only; no exchange-rate conversion is applied.
This mulch calculator works out how much mulch, topsoil or compost you need to cover one or more areas at a chosen depth. Volume equals area times depth, and one cubic yard equals 27 cubic feet. For example, a bed 10 feet by 4 feet covered 3 inches deep needs 10 cubic feet, which is about 0.37 cubic yards or 5 bags of 2 cubic feet.
How Much Mulch Do You Need?
Buying too little means a second trip, and buying too much leaves a pile on the driveway. Enter your measurements above and the calculator returns the volume in cubic yards, cubic feet, cubic metres and litres. It also shows how many bags to buy, and the estimated cost if you add your prices.
How to Use the Mulch Calculator
- Choose your units. Pick Imperial for feet and inches, or Metric for metres and centimetres.
- Pick the material. Select Mulch, Topsoil or Compost. The maths is the same, and only the labels change.
- Describe each area. Choose Rectangle, Circle, Triangle or Known area, then type the measurements. Use Known area when you already have the square footage or square metres.
- Add more areas. Press "Add area" for each extra bed, border or path. You can enter up to 12 areas, and the totals combine them.
- Set the depth. Type a depth or tap a preset. The 2, 3 and 4 inch buttons cover the most common choices.
- Add a safety margin. The allowance box adds a percentage for settling and waste, from 0 to 50 percent.
- Choose the bag size. Pick a common bag capacity or enter your own. The bag count is always rounded up.
- Add prices (optional). Enter a price per cubic yard, a price per bag, or both. The cost lines appear once a price is filled in.
Open "Show working" under the results to see every step with your own numbers.
How Deep Should Mulch Be?
Most beds need a layer between 2 and 4 inches (5 to 10 cm) deep. Coarse mulch like bark chunks, or a fast-rotting type like fresh wood chips, can go up to 6 inches (15 cm). Thin layers let weeds through, while very thick layers can hold too much water and starve roots of air. Keep mulch a few inches away from tree trunks and plant stems. This depth advice is general guidance and is not calculated by the tool.
| Depth | Volume for 100 square feet | Cubic yards | 2 cubic foot bags |
|---|---|---|---|
| 2 inches | 16.67 cubic feet | 0.62 | 9 |
| 3 inches | 25 cubic feet | 0.93 | 13 |
| 4 inches | 33.33 cubic feet | 1.23 | 17 |
| 6 inches | 50 cubic feet | 1.85 | 25 |
Can I Use It for Topsoil and Compost?
Yes. Switch the material to Topsoil or Compost and enter the area and depth you want to cover. The calculator gives the volume you would order, in the same units. Soil and compost settle after spreading, so a 5 or 10 percent allowance is a sensible starting point. Planning a whole vegetable bed? The Garden Planner Calculator works out soil and compost volume for raised beds.
Mulch Formulas
Every figure on this page comes from three short rules.
- Volume = area × depth. Convert the depth to feet first: 3 inches is 0.25 feet.
- Circle area = π × (diameter ÷ 2)². Triangle area = base × height ÷ 2.
- Cubic yards = cubic feet ÷ 27. Bags = volume ÷ bag size, rounded up.
One cubic yard covers about 324 square feet at 1 inch deep. Dividing 324 by your depth in inches gives the coverage for any layer: 162 square feet at 2 inches, 108 at 3 inches, 81 at 4 inches and 54 at 6 inches. In metric, one cubic metre covers 10 square metres at 10 cm deep. Need other conversions? Try the Scientific Unit Converter.
Worked Examples
A small flower bed
A bed 10 feet long and 4 feet wide has an area of 40 square feet. At 3 inches deep, the volume is 40 × 0.25, which makes 10 cubic feet. That equals 0.37 cubic yards, so you need 5 bags of 2 cubic feet.
A large border with bulk delivery
A border 20 feet by 15 feet covers 300 square feet. At 3 inches deep it needs 75 cubic feet, or 2.78 cubic yards. With 2 cubic foot bags you would buy 38, and with 3 cubic foot bags you would buy 25. At a bulk price of $40 per cubic yard, the delivery costs $111.11. Buying 38 bags at $4.50 each costs $171, so bulk wins by a wide margin here.
A round bed
A circular bed 8 feet across has a radius of 4 feet, so its area is π × 16, or 50.27 square feet. At 2 inches deep the volume is 8.38 cubic feet. That is 0.31 cubic yards, or 5 bags of 2 cubic feet.
Adding an allowance
Take the 20 by 15 foot border again, with 10 percent extra. The volume rises from 75 to 82.50 cubic feet, or 3.06 cubic yards. The bag count goes from 38 to 42.
A metric yard
A bed 5 metres by 2 metres has an area of 10 square metres. Spread 7.5 cm deep, it needs 0.75 cubic metres, which is 750 litres. With 50 litre bags you would buy 15.
Types of Mulch
Mulches fall into two groups. Organic mulches such as shredded bark, bark chunks, wood chips, pine bark, cocoa shells and compost break down over time and feed the soil. Inorganic mulches such as gravel do not break down, so they need less topping up. Colour, texture and price differ between products, but the volume calculation is identical for all of them.
Bulk or Bagged Mulch?
Bulk mulch is sold by the cubic yard and usually costs less per unit once you need more than a few yards. Bagged mulch is easier to carry and store, and it suits small beds. Compare both lines in the results, then check your supplier's own bag size and delivery fees.
Common Mistakes to Avoid
- Measuring depth in inches but entering the figure as feet
- Forgetting to subtract the area under trees, paths or stones
- Rounding the bag count down
- Skipping the allowance on a soil or compost order
- Assuming every bag holds 2 cubic feet when your supplier's bags are a different size
Frequently Asked Questions
How many cubic yards of mulch do I need?
Multiply the area in square feet by the depth in feet, then divide by 27. For a 100 square foot bed at 3 inches deep, that is 100 × 0.25 ÷ 27, which gives 0.93 cubic yards.
How deep should I spread mulch?
Most beds do well with 2 to 4 inches. Coarse or fast-rotting mulch can go up to 6 inches.
How do I calculate mulch for a round bed?
Choose Circle and enter the diameter. The calculator finds the radius, works out the area as π × radius², and multiplies by your depth.
How many bags make a cubic yard?
A cubic yard holds 27 cubic feet, so it equals 13.5 bags of 2 cubic feet. Round up to 14 bags if you want to cover a full cubic yard.
How much area does one cubic yard cover?
It covers about 324 square feet at 1 inch deep. At 3 inches deep it covers about 108 square feet.
Can I use the calculator for topsoil or compost?
Yes. Change the material to Topsoil or Compost. The volume maths is the same as for mulch.
Should I order extra?
A small allowance of 5 to 10 percent covers settling, uneven ground and waste. You can set it from 0 to 50 percent.
Does the calculator work in metric units?
Yes. Switch to Metric to enter metres and centimetres, and read the results in cubic metres and litres as well as cubic yards.
Does the calculator save my measurements?
No. Nothing is stored, so use "Copy results" before you leave the page.
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