The Formula Behind This Calculator
Volume (cu ft) = bed length x bed width x (depth in inches / 12)
Cubic yards = volume (cu ft) / 27
Bags = round up (volume (cu ft) / bag size (cu ft))
Mulch math is pure volume: the footprint of the bed times the depth you spread. The only trap is units. Depths are chosen in inches, bags are sold in cubic feet, and bulk mulch is sold in cubic yards of 27 cubic feet, so a single estimate has to speak all three languages at once, which is exactly what the results above do. One more practical note: bagged mulch is measured loose in the bag, and it settles as you spread and water it, so the estimate assumes a freshly spread depth. If your beds are thirsty and uneven, the 4 inch setting gives you a buffer without a second trip.
Worked Example: A 20 by 4 Foundation Bed at 3 Inches
A planting bed along the front of a house is 20 feet long by 4 feet wide, and you are refreshing it at the standard 3 inch depth with 2 cubic foot bags.
- Bed area: 20 x 4 = 80 square feet.
- Volume: 80 x (3 / 12) = 80 x 0.25 = 20 cubic feet.
- Bags: 20 / 2 = 10 bags exactly.
- Bulk equivalent: 20 / 27 = 0.74 cubic yards.
- Budget: 10 bags at $3 to $5 is $30 to $50 bagged. The same mulch in bulk is about $22 to $33 worth of material, but most yards charge a delivery fee or a minimum, so bags win at this size.
Scale that bed up by four, front and back of the house, and the picture flips: 40 bags at $120 to $200 against about 3 bulk yards at $90 to $135 plus delivery. The crossover in this example lands around 14 bags, which matches the FAQ guidance and is worth checking with your own bed sizes before you load a cart.
A Complete Guide to Estimating Mulch for Any Bed
Mulch looks like the simplest purchase in the garden center, a pile of bags and a sunny Saturday. In practice it is the most commonly underestimated material in landscaping, because depth multiplies quietly: one inch over a large bed is a lot of bags. This guide covers measuring odd shaped beds, choosing a depth with a purpose, and the bagged versus bulk decision with real numbers.
Measure Beds That Are Not Rectangles
Most beds curve. For a wavy bed, measure the length along the curve and take the width at three or four points, then use the average width: the estimate lands within a bag or two, which the rounding covers. For a circle, such as a tree ring, area is 3.14 times the radius squared, so a 6 foot ring (3 foot radius) is about 28 square feet. Kidney and island beds can be split into rough rectangles and half circles on paper. Resist the urge to measure only the empty soil you can see: mulch goes under the shrubs too, right up to the house and the edging, so measure the full bed outline and let the plant canopies hide their share.
Depth Is a Decision, Not a Default
Depth does three jobs: weed suppression, moisture retention and looks. Two inches is a cosmetic refresh over existing mulch that is still mostly intact. Three inches is the working standard for established beds, thick enough to shade out most weed seed. Four inches suits a new bed, a bed converted from lawn, or a slope where rain moves mulch downhill. More is not better: past about 4 inches, mulch can shed water instead of absorbing it, and fine shredded mulch packed too deep can mat and sour. Remember that mulch decomposes from the bottom up, feeding the soil, so a bed mulched at 3 inches wants a 1 to 2 inch top up each year rather than a full redo.
What Mulch Costs in 2026
As of October 2026, standard shredded hardwood or pine bark mulch in 2 cubic foot bags runs about $3 to $5 a bag at national home centers, with dyed black, brown and red mulch in the same range and cedar or pine straw costing more. Bulk mulch from a landscape supply yard commonly runs $30 to $45 per cubic yard picked up, with delivery adding $50 to $100 depending on distance, and many yards set a 2 or 3 yard delivery minimum. Rubber mulch is the expensive outlier at several times the price, sold for playgrounds and permanent beds. For a typical suburban home with 300 square feet of beds at 3 inches, budget roughly $90 to $150 in bags or a similar total in bulk once delivery is counted.
Spreading Habits That Stretch Your Mulch
- Edge the bed first with a clean trench edge: it holds mulch in and makes the bed look finished at any depth.
- Spread by the bucket or wheelbarrow load across the whole bed thinly, then add the second pass to depth, rather than finishing one end deep.
- Keep mulch 3 to 6 inches back from trunks and crowns, and pull it away from house siding and vents.
- Water lightly after spreading to settle fines and reduce wind drift on the first dry week.
- Note your bed sizes and bag count in a garden log. Next year's refresh becomes a five minute order, not a fresh estimate.