How Much Mulch Do I Need? (2026 Calculator + Coverage Chart)
Figuring out how much mulch to buy looks simple until you are standing in the garden centre staring at a pallet of bags. Buy too little and you are back in the car mid-project. This guide gives you the exact method, plus our free Mulch Calculator for your own bed size.
How much mulch do I need for my garden bed?
Multiply length by width to get the area, then multiply by depth in feet. A 20 by 10 foot bed at 3 inches needs 50 cubic feet of mulch, which is 25 standard 2 cubic foot bags or 1.85 cubic yards. The Mulch Calculator does this for any size and depth, and compares bag and bulk prices.
The steps are area equals length times width, and volume equals area times depth in inches divided by 12. Divide cubic feet by 27 for cubic yards.
How many bags of mulch do I need?
Divide your total cubic feet by the bag size, then round up. A 20 by 10 foot bed at 3 inches needs 50 cubic feet, so that is 25 bags of 2 cubic foot mulch, or 17 bags of 3 cubic foot mulch. If the total is 26.3 bags, buy 27, because you cannot buy part of a bag.
Always read the label before counting. Most bags hold 2 cubic feet, but 3 cubic foot and 1.5 cubic foot bags are common too.
How far does one cubic yard of mulch cover?
One cubic yard covers 162 square feet at 2 inches deep, 108 square feet at 3 inches, and 81 square feet at 4 inches. The rule is 27 divided by depth in feet, so 27 divided by 0.25 feet gives 108 at 3 inches.
Garden centres often quote about 100 square feet at 3 inches, a rounded, slightly short version of the exact 108 figure.
How deep should mulch be?
Three inches is the standard depth for garden beds, deep enough to suppress weeds and hold moisture while letting water and air reach the roots. Two inches suits a top-up over existing mulch, and four inches suits new beds or heavy weed pressure. Never go deeper than four inches, and keep mulch away from tree trunks and stems.
Measure only the depth you want to add. If two inches of old mulch remain and you want three inches total, you only need to add one inch.
Should I buy bags or bulk mulch?
Bags are usually better for small jobs under about one cubic yard, while bulk mulch is almost always cheaper per cubic foot for larger jobs. The crossover depends on delivery fees: a bulk delivery charge can erase the saving on a small order, while bags need no delivery or minimum order. The Mulch Calculator compares both for your exact volume.
Access matters too. Bulk mulch arrives as a pile on a driveway and must be wheelbarrowed to the bed, while bags can be carried one at a time to wherever they are needed.
Should I order extra mulch?
Ordering about 10% extra is sensible for curved, sloped, or uneven beds, because mulch settles over the first few weeks and some always spills during spreading. The calculator deliberately does not add this buffer, so its number is the exact volume for your stated dimensions. To add it yourself, multiply the bag count by 1.1 and round up.
For a neat rectangular bed on flat ground the buffer is optional. For a bed with curves, a slope, or roots pushing the surface up, it saves a return trip: 25 bags plus 10% is 27.5, so buy 28 bags.
How do I measure an irregularly shaped bed?
Split the bed into rectangles and circles, work out each area, and add them together. A rectangle’s area is length times width, and a circle’s area is 3.14 times the radius squared. Then use that total area with your chosen depth in the Mulch Calculator, or apply the coverage table directly to the total.
L-shaped beds are the most common irregular shape: split the L into two rectangles at the inside corner and add them. For a wavy edge, use the average width measured at several points.
How much does mulching a garden bed cost?
Bagged mulch typically costs $3 to $6 per 2 cubic foot bag, so a 20 by 10 foot bed at 3 inches costs roughly $75 to $150 in bags. Bulk mulch typically costs $25 to $50 per cubic yard, so the same bed costs roughly $46 to $93 in bulk before delivery fees, which commonly run $25 to $75.
Spreading a cubic yard yourself takes most people 30 to 60 minutes; hiring it out usually adds $50 to $100 per cubic yard for labour. For the bigger numbers around the same property, see our Mortgage Payment Calculator and Homeowners Insurance Cost Estimator.
When is the best time to mulch?
Late spring, after the soil has warmed and before summer heat arrives, is the best time for most gardeners. Spring mulching locks in moisture ahead of the hottest months and suppresses the first weeds. Autumn is the second-best window, because mulch insulates soil through winter and breaks down into organic matter by spring.
Plant first, then mulch around the new plants, rather than mulching the whole bed and digging through it. Avoid mulching frozen or waterlogged ground.
Frequently Asked Questions
How many bags of mulch are in a cubic yard? A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cubic foot mulch, or 9 bags of 3 cubic foot mulch. Buy 14 two-cubic-foot bags to cover a full cubic yard.
How much mulch do I need for a 10 by 10 foot bed? At 3 inches deep, a 10 by 10 foot bed is 100 square feet and needs 25 cubic feet, which is 13 standard 2 cubic foot bags or 0.93 cubic yards.
Can I put new mulch over old mulch? Yes, as long as the total depth stays at or under 4 inches. If old mulch has already built up to 3 or 4 inches, rake it loose or remove some before adding more.
How often should I replace mulch? Most organic mulch needs topping up once a year, usually in spring, when the depth has dropped below 2 inches.
Disclaimer: This guide gives estimates only. Actual mulch needs vary with bed shape, settling, and spreading technique, and prices vary by supplier and region. Measure your own beds and confirm local prices before ordering.
