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?
Don’t be left wondering how mulch is too mulch! With our handy calculator, you can work out how much mulch you need without even having to get your hands dirty. Once calculated, you can make your trip to Home Depot, Lowes or your local garden centre safe in the knowledge of how much mulch you need to buy.
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. All that and a killer onomatopoeic name!
But you don’t want to shell out much too much for too much mulch…
Before we discuss how to measure the ground you're aiming to cover, here's a quick chart of coverage for standard US mulch bag sizes for mulch depth of 1-4 inches.
|Desired depth||3 cu.ft. bag||2 cu.ft. bag||1 cubic yard|
|1"||36 sq.ft||24 sq.ft||324 sq.ft|
|2"||18 sq.ft||12 sq.ft||162 sq.ft|
|3"||12 sq.ft||8 sq.ft||108 sq.ft|
|4"||9 sq.ft||6 sq.ft||81 sq.ft|
Measuring and calculating for mulch coverage
Whether it’s a flower bed, playground or pathway, you need to know how much ground you’re aiming to cover. Here's a quick how-to guide on measuring and calculating.
1. 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
2. Do the math
length × width × depth = volume
US imperial example
20ft × 8ft × 0.25ft = 40 cubic feet
UK metric example
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.
So covering your garden is simple… Mulch ado about nothing, really!
If you have any problems using this mulch calculator, please contact me.