Mulch Calculator
Disclaimer: Whilst every effort has been made in building our calculator tools, we are not to be held liable for any damages or monetary losses arising out of or in connection with their use. Full disclaimer.
How much mulch do I need?
Mulch is commonly sold in cubic yards. One cubic yard of mulch is enough to cover an area of 324 square feet at 1 inch of depth or 162 square feet at 2 inches of depth.
Coverage for 1 cubic yard of mulch
| Desired depth | Sq.ft coverage | Approx coverage |
|---|---|---|
| 1 inch | 324 sq.ft | 18' × 18' |
| 2 inches | 162 sq.ft | 13' × 13' |
| 3 inches | 108 sq.ft | 11' × 10' |
| 4 inches | 81 sq.ft | 9' × 9' |
Alongside a good kneeling mat and a horde of aphid-hungry ladybirds, mulch can be a gardener’s best friend. Usually made with bark chips (but sometimes also straw, rubber, hardwood or gravel), it’s the perfect top layer for flowerbeds: mulch keeps moisture in, deters nuisance weeds from sprouting out, and can provide a tidy-looking finish for bedded areas.
If you're wondering how to calculate the right amount of mulch needed for your garden, we're here to help. Assuming you know the square footage of the area needed to be covered, you can use this formula:
The above formula helps you find out how many cubic yards of mulch you might need, but you may be buying your mulch by the bag, which is commonly sold in cubic feet in the US and in liter/litre bags in the UK. So, let's look at some measurement conversions.
How many cubic feet is in a yard of mulch?
A cubic yard of mulch measures 27 cubic feet. A standard bag of mulch in the US holds 2 cubic feet. This means you need 13 1/2 bags to make up a cubic yard.
Mulch can be sold in both large and smaller-sized bags, so let's go through the most common sizes.
How many 2 cubic feet bags of mulch make a yard?
Most standard bags of mulch hold 2 cubic feet. As there are 27 cubic feet in a cubic yard, a cubic yard of mulch equates to 13 1/2 bags.
How many 3 cubic feet bags of mulch make a yard?
For bags of mulch measuring 3 cubic feet, a cubic yard of mulch will equate to 9 bags (there are 27 cubic feet in a yard).
How many 1.5 cubic feet bags of mulch make a yard?
For 1.5 cubic foot bags of mulch, a cubic yard of mulch equates to 18 bags (there are 27 cubic feet in a yard).
Summary of bag sizes for 1 cubic yard
To summarize, 1 yard of mulch equals:
- 27 bags of 1 cu.ft size.
- 18 bags of 1.5 cu.ft size.
- 13 1/2 bags of 2 cu.ft size.
- 9 bags of 3 cu.ft size.
If you want to manually calculate the number of bags of mulch you require to cover an area in square feet, here's how to do it...
Calculating from square feet
To calculate the number of bags you need to buy for an area of square feet, multiply your square feet figure by the depth of mulch required in inches, divide it by 12 and then divide it by the bag size (in cubic feet).
Mulch coverage per bag
To help you with your calculations, here's a quick chart of coverage for standard US mulch bag sizes for mulch depth of 1-4 inches. We'll then cover the process of measuring and calculating how much mulch you might need in more detail.
Coverage for 2 cu.ft bag of mulch
| Desired depth | Coverage per bag |
|---|---|
| 1 inch | 24 sq.ft |
| 2 inches | 12 sq.ft |
| 3 inches | 8 sq.ft |
| 4 inches | 6 sq.ft |
Coverage for 3 cu.ft bag of mulch
| Desired depth | Coverage per bag |
|---|---|
| 1 inch | 36 sq.ft |
| 2 inches | 18 sq.ft |
| 3 inches | 12 sq.ft |
| 4 inches | 9 sq.ft |
Coverage for 100 litre bag of mulch
In the UK, mulch is sold in litre bags. Here are conversions for 100 litre mulch bags.
| Desired depth | Coverage per 100L bag |
|---|---|
| 1 inch | 42 sq.ft |
| 2 inches | 21 sq.ft |
| 3 inches | 14 sq.ft |
| 4 inches | 11 sq.ft |
Guide to measuring and calculating mulch
Whether it’s a flower bed, playground or pathway, you need to know how much ground you’re aiming to cover with your mulch. Here's an in-depth guide on how to measure and calculate.
1) Measure your area
It's key that you work with the same unit the whole time: don’t measure one aspect in feet, another in inches, and the other in cm! US gardeners are safest with feet, whilst British gardeners should probably work in metres or centimetres, but just pick one and stick to it.
Measure the length and width of the area for mulching. If it’s too large for a tape measure, just lay a length of twine along each side, trimming to fit, and measure the pieces of twine afterwards to get their dimensions. If it’s an irregular shape, break it up into squares or rectangles and take their measurements individually. If it’s a circular area, you can treat it like a square that fits around the circle (don’t worry about the corners being extra; it’s always better to have some spare mulch anyway). If you want to get the precise area of your circle, though, use our square footage calculator here.
You also need to think about depth. If the mulch is going to be mainly decorative, then 2 inches is fine. If you’re hoping to retain moisture in a dry climate, or to block sunlight from reaching particularly persistent weeds, then you want 4 inches. If you’re not sure, take the middle ground and use 3 inches. Remember to use the same unit throughout your calculations, so convert inches to feet if that’s what you’re using.
- 2” = 0.17 feet or 0.051 metres
- 3” = 0.25 feet or 0.076 metres
- 4” = 0.33 feet or 0.102 metres
2) Do the math
To work out the volume of mulch you need, just multiply the three measurements together.
length × width × depth = volume
20ft × 8ft × 0.25ft = 40 cubic feet
6.09m × 2.44m × 0.076cm = 1.13 cubic metres
If you’ve taken individual measurements for an irregular shaped area, calculate the volume of each shape separately and then add the totals together to get your volume.
3) Check the sales unit
In the US, you might buy mulch by the cubic foot. If you followed the steps above using feet, then you already have the quantity worked out. If you’re buying a larger amount, it might be sold in cubic yards, so you may need to convert your volume:
- cubic yards = cubic feet / 27
- cubic feet = cubic inches / 1728
In the UK, mulch is usually sold in litres. One cubic meter is equivalent to 1000 litres, which is a common size for sacks of mulch. Additionally, each product typically lists its square-metre coverage, which means the shop has already factored in the depth. In this case, you simply multiply the width by the length of the ground, and use this area to compare with the product’s m² figure.
If you want to find out how much your mulch order is likely to weigh, we've got an article covering the weight of a cubic yard of mulch here.
So covering your garden is simple… Mulch ado about nothing, really!
For advice about the different types of mulch and tips for how to apply it, we recommend this article from Gardener's World.
To check your calculations, use the mulch calculator at the top of this page.
Calculator created by Alastair HazellIf you have any problems using our mulch calculator, please contact us.