How to use the mulch calculator
- Pick a mulch type — hardwood or pine bark, since they weigh different amounts.
- Choose a shape (rectangle, circle, triangle, or a ring for around a tree) and enter your bed's dimensions.
- Enter the depth you plan to spread — 2 to 4 in for most beds.
- Have more than one bed? Press Add another area to add them together.
- Read the result in cubic yards, cubic feet and bags (2 or 3 cu ft), tick a waste allowance, and enter a price for an estimated cost.
Don't know the square footage of your beds yet? The square footage calculator can help you measure first.
How much mulch do I need? The formula
Cubic yards = length (ft) × width (ft) × depth (ft) ÷ 27.
- Measure length and width in feet, and decide the depth in inches.
- Multiply length × width × (depth ÷ 12) to get cubic feet.
- Divide by 27 for cubic yards, or use the bag counts directly if you're buying bagged mulch.
Worked example: a 10 × 6 ft bed at 3 in deep needs 10 × 6 × (3 ÷ 12) = 15 cu ft, ÷ 27 = 0.56 cubic yards. That's 8 bags at 2 cu ft each, or 5 bags at 3 cu ft each — always rounded up.
Mulch types and recommended depth
| Mulch type | Typical density | Recommended depth | Notes |
|---|---|---|---|
| Hardwood mulch | 0.25 tons/yd³ | 2–4 in | Garden beds and around trees: 2–4 in deep, kept a few inches off the trunk. |
| Pine bark mulch | 0.2 tons/yd³ | 2–4 in | Lighter and fluffier than hardwood: 2–4 in deep. |
Typical, widely published values — density depends on moisture and how loosely the mulch is piled. Ask your supplier for their exact figure.
Bags vs. bulk mulch
Bagged mulch (usually 2 or 3 cu ft bags) is easy to carry and store, and works well for small beds or touch-ups. Bulk mulch, delivered by the cubic yard, is cheaper per cubic foot once you're covering more than a couple of beds — a 30 × 20 ft yard at 3 in deep needs about 5.56 cubic yards, which most suppliers would deliver in bulk rather than sell as 50 separate bags. Use the calculator's bag counts to compare the two: multiply the bag count by your local bag price and compare it to a bulk quote per cubic yard.
How deep, and how often
Aim for 2–4 in over most beds — enough to block weeds and hold moisture, without smothering roots or trapping moisture against stems. Because organic mulch breaks down and settles, most gardens need a top-up once a year, usually in spring; measure the existing depth first so you only order enough to bring it back up to your target depth rather than a full fresh layer every time.
Other landscaping calculators
- Laying gravel paths between the beds? Try the gravel calculator.
- Filling beds with topsoil or garden soil first? Try the topsoil calculator.
- Setting pavers nearby? Try the sand calculator.
- Just need the area, not the material? Try the square footage calculator.
Frequently asked questions
How much mulch do I need?
Multiply the bed's area in square feet by the depth in feet, then divide by 27 for cubic yards. A 10 × 6 ft bed at 3 in deep needs 15 cubic feet, which is 0.56 cubic yards. The mulch calculator above does the maths for any shape, in bulk or in bags.
How deep should mulch be?
Most garden beds and around trees and shrubs want 2–4 in of mulch. Less than 2 in doesn't suppress weeds well, and piling on more than 4 in (especially against a trunk, sometimes called a "mulch volcano") can trap moisture and encourage rot, so keep mulch a few inches back from stems and trunks.
How many bags of mulch do I need?
Bagged mulch is usually sold in 2 cu ft or 3 cu ft bags. The 10 × 6 ft bed above (15 cu ft at 3 in deep) needs 8 bags at 2 cu ft each, or 5 bags at 3 cu ft. The calculator always rounds bags up, so you won't come up short on the last bag.
Should I buy mulch in bulk or in bags?
Bags are convenient for small beds and easy to carry, but bulk (by the cubic yard) is almost always cheaper for larger areas — typically once you need more than about 2–3 cubic yards. A 30 × 20 ft yard at 3 in deep needs about 5.56 cubic yards, which is usually worth ordering in bulk rather than as 50 individual 3 cu ft bags.
How much does one cubic yard of mulch cover?
One cubic yard covers about 324 sq ft at 1 in deep, 162 sq ft at 2 in, 108 sq ft at 3 in, or 81 sq ft at 4 in (324 ÷ depth in inches). Enter your own depth in the calculator above for an exact figure for your bed.
How often should I re-mulch?
Organic mulch (bark or wood chips) breaks down over time, so most beds need topping up once a year, typically in spring. If the existing layer has settled to under 2 in, add enough fresh mulch to bring it back up to 2–4 in rather than removing the existing layer.
What is the 3-3-3 rule for mulch?
It is a rule of thumb for mulching around trees: keep mulch about 3 in deep, in a ring roughly 3 ft wide around the trunk, and at least 3 in away from the trunk itself so the bark can breathe. It helps avoid piling mulch against the trunk ("mulch volcanoes"), which can trap moisture and invite rot and pests.
How much mulch do I need for a ring around a tree?
Use the "Ring" shape and enter the outer and inner diameter — the inner diameter is roughly the trunk's width or the bare space you want to leave. An 8 ft outer ring with a 1 ft gap at 3 in deep needs about 12.37 cubic feet (0.46 cu yd) of mulch.
What's the difference between hardwood and pine bark mulch?
Hardwood mulch is denser (about 0.25 tons per cubic yard) and breaks down into the soil faster, adding nutrients as it composts. Pine bark mulch is lighter (about 0.2 tons per cubic yard), holds its color longer and resists compaction, which some gardeners prefer for slopes and paths. Both are entered as separate options in the calculator, since the weight differs.
Is my data saved or sent anywhere?
Your measurements are saved only in your own browser, so they are there next time you open this page on the same device. Nothing is sent to our servers.