How to use this calculator
- 1Measure the length and width of the bed, or enter the total area if you already know it.
- 2Enter the depth you want once the mulch is spread. 2–3 inches (5–7.5 cm) suits most beds.
- 3Choose your bag size, or type the volume printed on the bag.
- 4Keep the 10 % extra for settling, or change it if you prefer.
- 5Read off the cubic yards or cubic metres (for a bulk delivery) and the number of bags.
The formula
- 01Area = length × width
- 02Mulch = area × depth × (1 + extra %)
- 03Bags = mulch ÷ volume of one bag, rounded up
- 041 cubic yard = 27 cubic feet ≈ 0.765 m³ · 1 m³ = 1,000 litres
The depth has to be in the same unit as the area before you multiply: in feet for square feet (3 in = 0.25 ft) or in metres for square metres (75 mm = 0.075 m). That is why one cubic yard (27 ft³) covers about 108 ft² at 3 inches deep, and one cubic metre covers about 13 m² at 75 mm.
Mulch settles as it dries and breaks down, and it never spreads perfectly evenly, so the calculator adds 10 % by default. In a University of Florida study, woody mulches spread 9 cm (3.5 in) deep kept about two thirds of their depth after two years, while pine straw lost half its depth in the first year.
Bagged mulch is sold by volume, not by weight: the bag says 2 cu ft, 3 cu ft or a number of litres. Bulk mulch is sold by the cubic yard in the US and by the cubic metre or bulk bag in the UK and Europe, which is why the result is shown in both.
Worked example
A 20 ft × 5 ft bed is 100 ft². At 3 in deep with 10% extra for settling, it needs 1.02 yd³ of mulch (27.5 ft³).
In 2 ft³ bags that is 14 bags; for a bulk delivery, order 1.02 yd³.
Tips before you buy
- Pull the weeds and water the soil before you mulch. Mulch keeps moisture in and stops new weed seeds, but it will not smother established perennial weeds.
- Use a thinner layer of fine mulch such as shredded leaves or compost (1–2 in, 2.5–5 cm) and a thicker layer of coarse bark or wood chips (2–4 in, 5–10 cm).
- Leave a ring of bare soil around every tree: Penn State Extension suggests 3–5 in (8–12 cm) for young trees and 8–10 in (20–25 cm) for mature ones. Never build a cone of mulch around a trunk.
- Several beds? Work out the area of each one, add them up and enter the total with “Enter the area”. Our square footage calculator can add up odd shapes for you.
- For bigger jobs, compare the price per cubic yard or cubic metre: divide the bag price by the volume printed on the bag. Bulk delivery is often cheaper for large areas and saves a lot of plastic bags.
Frequently asked questions
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cu ft (buy 14), 9 bags of 3 cu ft or 18 bags of 1.5 cu ft. In metric, a cubic metre is 1,000 litres: about 17 bags of 60 litres or 13 bags of 80 litres.
How much area does a cubic yard of mulch cover?
About 324 ft² at 1 inch deep, 162 ft² at 2 inches, 108 ft² at 3 inches and 81 ft² at 4 inches. A cubic metre covers about 20 m² at 50 mm deep or 13 m² at 75 mm.
How deep should mulch be?
2–3 inches (5–7.5 cm) suits most beds. Penn State Extension recommends 2–4 inches of organic mulch and no more, and less on poorly drained soil. The RHS recommends at least 5 cm, ideally 7.5 cm, for mulches such as bark.
How much does one bag of mulch cover?
A 2 cu ft bag covers 12 ft² at 2 inches deep or 8 ft² at 3 inches. A 60 litre bag covers about 1.2 m² at 50 mm or 0.8 m² at 75 mm. Deeper layers cover less, so always calculate with the depth you really want.
Should I remove old mulch before adding new mulch?
Not always. If the old layer is still 2–3 inches deep, fluff it up or add a thin top-up. If it has matted down or built up past about 4 inches, rake some off first. Penn State Extension warns that adding new mulch over old every year is the same as applying too deep a layer all at once.
Is it cheaper to buy mulch in bags or in bulk?
It depends on local prices, so compare the price per cubic yard or cubic metre. Bags are easy to carry and store for small beds. Bulk mulch is usually sold by the cubic yard or bulk bag, often with a delivery charge, and you need space for the pile.
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Sources
- Penn State Extension – Mulching landscape trees (2–4 in and no more; keep mulch off the trunk)
- RHS – Mulches and mulching (at least 5 cm, ideally 7.5 cm)
- University of Florida IFAS – Landscape mulches: how quickly do they settle?
- Mulch Mound – How to measure for mulch (“add 10 % to your total”)
Formulas last reviewed: September 30, 2026 ·How we check our formulas