Mulch Calculator
Work out exactly how much mulch to buy before you head to the garden centre. Enter the bed dimensions or area and the depth you want, then get the volume in cubic yards and cubic feet, the number of bags at two common sizes, an estimated weight, and an optional cost breakdown for both bagged and bulk mulch.
Formula
Worked example
A 100 ft² bed at 3 in deep with 10% waste: 100 × (3 ÷ 12) = 25 cu ft net. Add 10%: 27.5 cu ft, 27.5 ÷ 27 = 1.02 cu yd. Bags: ceil(27.5 ÷ 2) = 14 bags (2 cu ft) or ceil(27.5 ÷ 3) = 10 bags (3 cu ft). Weight at wood chip density 20 lb/cu ft: 550 lb.
How to calculate how much mulch you need
Mulch is sold by volume, so the core calculation is simply area times depth. Measure the length and width of each bed to get the area, decide how deep a layer you want, then multiply. The depth must be in the same units as the area dimension: if area is in square feet, convert depth from inches to feet by dividing by twelve before multiplying. The result is cubic feet, and dividing by 27 converts that to cubic yards, the unit most landscape suppliers quote for bulk orders. This calculator also accepts total area directly if you already know it, and it works in metric too.
Waste allowance, bags, weight and cost
Garden beds are never perfectly square, mulch settles by 10-20% in its first season, and edge spillage is common, so adding 10% extra is a practical rule. The calculator applies your chosen allowance before working out bags. Standard bags are 2 cubic feet (roughly 50 litres) or 3 cubic feet; one cubic yard holds 13.5 two-cubic-foot bags or 9 three-cubic-foot bags. Weight varies significantly by type: light materials like straw and pine needles weigh under 10 lb per cubic foot, while rubber mulch can reach 65 lb per cubic foot. The optional cost estimator lets you compare bagged price (per bag) against bulk delivery price (per cubic yard) so you can pick the better deal for your quantity.
Choosing the right depth and type
Two to three inches suits most ornamental flower beds, providing enough coverage to suppress weeds and hold moisture without smothering shallow roots. Around trees and shrubs, three to four inches is better for weed control and insulation, but keep mulch pulled back from the base of the trunk to prevent rot. On slopes, a coarser bark nugget holds position better than fine chips. Straw is popular in vegetable gardens because it decomposes quickly and adds organic matter. Rubber mulch is long-lasting and stays put on playgrounds but does not improve soil. Whatever type you choose, avoid piling it deeper than four inches, and never "volcano mulch" around tree bases.
Bagged versus bulk mulch
For projects under about one cubic yard (27 cubic feet), bagged mulch from a home-improvement store is convenient: no delivery fee, easy to load in any car, and available in small increments. Above one yard, bulk mulch delivered by the truckload is almost always cheaper on a per-volume basis. A typical pickup truck bed holds two to three loose cubic yards. Bulk mulch is usually fresher and has a wider variety of materials than the bagged options at retail stores. Ask your supplier for a price per cubic yard including delivery, then compare that to the bags2 × price-per-bag figure from this calculator.
Coverage reference: bags and bulk
| Quantity | 2 in depth (5 cm) | 3 in depth (7.5 cm) | 4 in depth (10 cm) |
|---|---|---|---|
| 1 cu yd (27 cu ft) | 162 ft² (15 m²) | 108 ft² (10 m²) | 81 ft² (7.5 m²) |
| 13.5 bags (2 cu ft) | 162 ft² | 108 ft² | 81 ft² |
| 9 bags (3 cu ft) | 162 ft² | 108 ft² | 81 ft² |
| 1 bag (2 cu ft) | 12 ft² (1.1 m²) | 8 ft² (0.74 m²) | 6 ft² (0.56 m²) |
| 1 bag (3 cu ft) | 18 ft² (1.7 m²) | 12 ft² (1.1 m²) | 9 ft² (0.84 m²) |
| 5 cu yd bulk load | 810 ft² (75 m²) | 540 ft² (50 m²) | 405 ft² (38 m²) |
How much area common quantities of mulch cover at standard depths.
Frequently asked questions
How many bags of mulch equal one cubic yard?
One cubic yard equals 27 cubic feet. With the common 2-cubic-foot bag that is 13.5 bags; with the larger 3-cubic-foot bag it is 9 bags. The calculator rounds up to whole bags automatically so you never come up short.
How deep should mulch be?
Two to three inches (5-7.5 cm) is ideal for most flower and ornamental beds, and up to four inches around trees and shrubs. Avoid going deeper than four inches, as too thick a layer can block water and oxygen from reaching roots, and never pile mulch against a trunk or stem.
Should I order mulch in bags or in bulk by the yard?
For less than one cubic yard, bags are convenient and avoid a delivery fee. Above one cubic yard, bulk mulch by the truckload is almost always cheaper per unit of volume. A useful comparison: one cubic yard at $45 bulk costs $45, while covering the same volume with 2 cu ft bags at $5 each costs about $68. Use the cost estimator in this calculator to see the numbers for your own prices.
How do I account for mulch settling?
Fresh mulch typically settles 10-20% over its first season as it compresses and begins to decompose. Setting the waste allowance to 10-15% builds that into your order so you end up with the coverage depth you planned for. The calculator applies the allowance before working out bags and cubic yards.
How much does a cubic yard of mulch weigh?
Weight depends on the type: shredded hardwood or wood chips weigh roughly 400-600 lb per cubic yard, bark nuggets around 400-500 lb, pine needles around 200 lb, and rubber mulch can exceed 1,700 lb per cubic yard. The calculator estimates weight from the type you select so you can check vehicle payload limits before you load up.
Can this calculator handle circular or irregular beds?
Yes, by computing the area yourself first. For a circular bed, the area equals pi times the radius squared (about 3.14 × r²). For an L-shaped or irregular bed, break it into rectangles, work out each one, add them together, and type the total into the "total area" field.