Mulch Calculator
Estimate how much mulch you need, and compare the cost of bags with bulk delivery.
Results
| Item | Value |
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Quick Answer
Multiply length by width by depth in feet to get cubic feet, then divide by 27 for cubic yards. A 20 ft by 10 ft bed at 3 inches deep needs 50 cubic feet, which is 1.85 cubic yards or 25 bags of 2 cubic feet each.
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Adjust the size if needed, then copy the code below into your page or blog. The calculator will load in an iframe and stay updated automatically.
Table of Contents
How This Mulch Calculator Works
Mulch is sold by the bag or in bulk by the cubic yard. This calculator works out the volume of your bed, then shows how many bags you need and what each option could cost.
Quick explanation: Cubic feet = length × width × depth in inches ÷ 12.
- Depth: the layer of mulch, in inches.
- Bag size: many bags hold 2 cubic feet, but check the label.
- Prices: optional, to compare bags with bulk.
How to Use the Mulch Calculator
- Measure the length and width of your bed in feet.
- Enter the depth of mulch you want, in inches.
- Check the bag size on the label. Many hold 2 cubic feet.
- Optionally, enter a bag price and a bulk price per cubic yard.
- Press Calculate to see cubic yards, bags and the cost of each option.
Core Formulas
- Area: length × width
- Cubic feet: area × depth in inches ÷ 12
- Cubic yards: cubic feet ÷ 27
- Bags: cubic feet ÷ bag size, rounded up
One cubic yard is 27 cubic feet, because 3 ft × 3 ft × 3 ft = 27.
Worked Example
Your bed is 12 ft by 8 ft, and you want 2 inches of mulch from 2 cubic foot bags.
- Area = 96 sq ft
- Volume = 96 × 2 ÷ 12 = 16 cu ft
- Cubic yards = 16 ÷ 27 = 0.59 cu yd
- Bags = 16 ÷ 2 = 8 bags
Real-Life Examples
- Front yard beds: two beds of 30 ft by 4 ft at 3 inches need 60 cubic feet, which is 2.22 cubic yards or 30 bags of 2 cubic feet.
- Around a tree: a circle 8 ft across is about 50.3 sq ft. At 3 inches deep, that is about 12.6 cubic feet, or 7 bags. Keep the mulch a few inches away from the trunk.
- Topping up: if old mulch is still 1 inch deep and you want 3, enter 2 inches as the depth.
- A large garden: 500 sq ft at 3 inches is 4.63 cubic yards. At $35 a yard in bulk that is about $162, compared with about $252 for 63 bags at $4.
Bagged vs Bulk Mulch
- Bagged: easy to move and store, and good for small beds or top-ups.
- Bulk: often cheaper per cubic yard for big jobs, but you may pay for delivery and need space for the pile.
- Mess and effort: bags are cleaner to handle. Bulk needs a wheelbarrow and shovel.
- Compare: enter both prices above. The calculator shows both totals side by side.
Mulch Coverage by Depth
One cubic yard is 27 cubic feet.
| Depth | Area per cubic yard | 2 cu ft bags per 100 sq ft |
|---|---|---|
| 1 in | 324 sq ft | 5 |
| 2 in | 162 sq ft | 9 |
| 3 in | 108 sq ft | 13 |
| 4 in | 81 sq ft | 17 |
Planning Your Mulch
- Depth: check advice for your plants and mulch type.
- Trunks and stems: keep mulch from piling up against them.
- Bulk delivery: larger areas are often cheaper in bulk, but check the delivery fee.
- Odd shapes: split the bed into rectangles and add the results.
Common Mistakes to Avoid
- Piling mulch against trunks. Mulch volcanoes can hold moisture against bark. Leave a gap.
- Spreading it too thick. Very deep layers can keep water and air from reaching roots.
- Forgetting old mulch. Measure what is left and only add the difference.
- Guessing curved beds. Split them into rectangles and circles, then add the results.
- Ignoring delivery fees. They can make bulk more expensive for small orders.
Frequently Asked Questions
Multiply length, width and depth in feet to get cubic feet. Divide by 27 for cubic yards, or by your bag size for bags.
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cubic feet, or 14 if you round up.
At 3 inches deep, a cubic yard covers 108 square feet.
It depends on your local prices and delivery fees. Enter both prices above to compare.
Yes. Split the bed into rectangles, run each one, and add the results.
Many garden guides suggest about 2 to 4 inches for beds. Check advice for your plants and mulch type.
Organic mulch breaks down over time, so many people top it up once a year.
Many gardeners use straw, shredded leaves or compost, which break down and feed the soil. Avoid mulch that may contain treated wood.
At 2 inches deep, it covers 12 sq ft. At 3 inches, it covers 8 sq ft.
References & Sources
| Source | Used For | Link |
|---|---|---|
| NIST, Unit conversion | US customary length and volume units. | https://www.nist.gov/pml/owm/metric-si/unit-conversion |
| Wikipedia, Cubic yard | A cubic yard equals 27 cubic feet. | https://en.wikipedia.org/wiki/Cubic_yard |