Disclaimer: Whilst every effort has been made in building this calculator, we are not to be held liable for any damages or monetary losses arising out of or in connection with the use of it. This tool is here purely as a service to you, please use it at your own risk. Full disclaimer. Do not use calculations for anything where loss of life, money, property, etc could result from inaccurate calculations.
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 deep. To calculate how much mulch you need, you can therefore use the formula: Mulch required = Square footage of area × depth / 324.
Our formula above tells you how many cubic yards of mulch you might need, but you may be buying your mulch by the bag, which is often sold in cubic feet in the US and in liter/litre bags in the UK.
How many bags of mulch are in a yard?
Most standard bags of mulch in the US hold 2 cubic feet. As there are 27 cubic feet in a yard, a yard (cubic) of mulch equates to around 13 1/2 bags.
- 1 yard of mulch = 27 bags of 1 cu.ft size.
- 1 yard of mulch = 13 1/2 bags of 2 cu.ft size.
- 1 yard of mulch = 9 bags of 3 cu.ft size.
To calculate how many bags you might need for a set number of cubic yards of mulch, divide your cubic yards figure by the bag size. If you need to work out the number of bags of mulch you require to cover an area in square feet, here's how to do it...
Buying mulch in cubic foot bags (US)
To calculate the number of bags you need to buy, multiply your area in square feet by the depth of mulch required (also in feet) and then divide it by the bag size (in cubic feet). If your desired depth is in inches, divide it by 12 first to get the depth in feet.
Buying mulch in litre bags (UK)
To calculate how many 100L litre bags you might need, multiply your area in square feet by the depth of mulch required (also in feet) to get the number of cubic feet you require. Next, convert the figure to litres by multiplying by 28.32. Finally, divide your figure by 100 to work out the number of 100L bags required.
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
|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|
Coverage for 1 cubic yard of mulch
|Desired depth||Coverage per cu yd|
|1 inch||324 sq.ft|
|2 inches||162 sq.ft|
|3 inches||108 sq.ft|
|4 inches||81 sq.ft|
Measuring and calculating guide
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.
How to measure the 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
How to do the math
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.
Checking 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.
So covering your garden is simple… Mulch ado about nothing, really!Calculator created by Alastair Hazell
If you have any problems using this mulch calculator, please contact me.