Measure your beds, then calculate depth and coverage

To estimate mulch, you need three numbers: the length and width of each bed, and how deep you want the mulch layer. Multiply length by width to get square footage, then multiply that by the depth in feet. Most landscapers spread mulch 2 to 4 inches deep — 2 inches for maintenance, 3 to 4 inches for new beds or weed suppression. Mulch is sold by the cubic yard, and one cubic yard covers roughly 100 to 150 square feet at 2 inches deep, or 75 to 100 square feet at 3 inches deep.

The math is straightforward once you have your measurements. A bed that is 10 feet long and 5 feet wide is 50 square feet. At 3 inches deep, that bed needs about 0.5 cubic yards of mulch. If you have multiple beds, add up all the square footage first, then divide by the coverage rate for your chosen depth. Rounding up by half a yard accounts for settling and uneven ground.

Key Takeaways

  • Measure the length and width of each bed in feet, multiply them together to get square footage, then add all beds together.
  • One cubic yard of mulch covers approximately 100 to 150 square feet at 2 inches deep, or 75 to 100 square feet at 3 inches deep.
  • Convert your total square footage to cubic yards by dividing by the coverage rate that matches your desired depth.
  • Round up by 0.5 cubic yards to account for settling, compaction, and uneven ground that will use extra material.

How to measure irregularly shaped beds

Not every bed is a rectangle. For L-shaped or curved beds, break them into simpler shapes — rectangles and triangles — measure each piece separately, then add the square footage together. An L-shaped bed can be split into two rectangles. A triangular section uses the formula (base × height) ÷ 2. If a bed has a gentle curve, approximate it as a rectangle slightly smaller than the full outline, or measure the curve in sections.

For circular beds, measure the radius (the distance from the center to the edge) and use the formula π × radius². For a bed with a 5-foot radius, that is 3.14 × 25, or about 78 square feet. If you are not confident in your measurement, sketch the bed on graph paper, count the squares, and multiply by the scale of your grid. Overestimating by 10 to 15 percent is safer than running short.

Account for obstacles and existing plants

Subtract the square footage of trees, shrubs, and hardscape features that will not be mulched. A tree with a 2-foot-diameter trunk takes up about 3 square feet. A large shrub might be 4 to 6 square feet. If you are mulching around a patio or stepping stones, measure those areas and subtract them from your bed total. The goal is to calculate only the soil surface that will actually receive mulch.

If you are refreshing an existing bed that already has mulch, you do not need to fill it completely. A 1 to 2 inch top-up is usually enough to restore appearance and suppress new weeds. For a refresh, use half the cubic yardage you would for a new bed at the same depth.

Convert square footage to cubic yards

The conversion depends on your chosen depth. At 2 inches deep, divide your total square footage by 150 to get cubic yards (or by 100 for a more conservative estimate). At 3 inches deep, divide by 100 (or by 75 for conservative). At 4 inches deep, divide by 75 (or by 60 for conservative). The lower number gives you more material; the higher number assumes efficient spreading with minimal waste.

Example: You have 300 square feet of beds and want 3 inches of mulch. Divide 300 by 100, which gives you 3 cubic yards. If you divide by 75 instead, you get 4 cubic yards. The difference is whether you expect some settling and compaction or whether you want a fuller, fluffier layer. Most homeowners use the middle estimate and order 3.5 cubic yards to be safe.

Account for mulch settling and compaction

Fresh mulch settles over the first few weeks as it absorbs water and compacts under its own weight. You will lose roughly 10 to 20 percent of depth in the first month, depending on the mulch type and how much rain falls. Shredded hardwood mulch settles more than wood chips. If you want a 3-inch layer to remain after settling, order enough for 3.5 to 4 inches initially.

Mulch also breaks down over time. A layer that is 3 inches deep in spring may be 2 inches by late summer, especially in hot, wet climates. If you want consistent coverage year-round, plan to add a 1 to 2 inch refresh layer each spring or fall. This is cheaper than replacing the entire bed every two years.

Order slightly more than your estimate

Mulch is sold in whole cubic yards, and you cannot order 2.7 yards — you round up to 3. It is better to have leftover mulch than to run short and have to place a second order. Extra mulch can be stored in a dry spot for a few months, used to top up beds later, or spread thinly in pathways. Most suppliers charge per cubic yard, so ordering one extra yard costs less than a second delivery fee.

If you are ordering from a landscape supplier or big-box store, ask whether they charge for delivery and whether there is a minimum order. Some suppliers offer free delivery over a certain amount; others charge a flat fee regardless of quantity. Factoring in delivery cost may make it worth ordering slightly more material at once rather than making two trips.

Frequently Asked Questions

How deep should mulch be?

Most beds use 2 to 4 inches. Two inches is enough for maintenance and weed suppression in established beds. Three to four inches works better for new beds, areas with heavy weed pressure, or if you want a fuller appearance. Deeper than 4 inches can trap moisture and promote rot in plant stems, so avoid piling mulch against tree trunks or shrub bases.

Does mulch type affect how much I need?

Slightly. Shredded hardwood mulch compacts more densely than wood chips, so you may need slightly less volume to achieve the same visual depth. Bark mulch is lighter and fluffier, so a cubic yard covers more area but settles faster. For estimation purposes, use the standard coverage rates (100 to 150 square feet per cubic yard at 2 inches), then adjust by 10 percent if you know your mulch type is unusually dense or loose.

What if my beds are on a slope?

Measure the bed as if it were flat, using the actual ground distance, not the slope distance. Mulch will slide downhill slightly over time, so you may want to add 10 to 15 percent extra to account for migration. On steep slopes, consider using landscape fabric or edging to hold mulch in place and reduce the amount you need to reapply each year.

Can I estimate mulch without measuring every bed?

Not accurately. A rough visual estimate often leads to ordering too little or too much. Spending 15 minutes with a measuring tape and a calculator saves money and frustration. If you have a very large property, measure a representative section, calculate the coverage, then scale up for the rest — but still measure the major beds individually.

How much mulch do I need for a refresh?

For an existing bed with mulch already in place, measure the square footage and order 0.5 to 1 cubic yard per 100 to 150 square feet. This gives you a 1 to 2 inch top layer that restores appearance and suppresses new weeds without completely replacing what is already there. Refresh mulch every 12 to 18 months, depending on climate and mulch type.