Mulch & topsoil calculator
Tell it your bed size and depth, get exact cubic yards, plus a bag-vs-bulk alert so you don't overpay at the garden center.
Quick answer
How much mulch or topsoil do I need?
Intro
When to use this calculator
A 2 cubic foot bag of mulch covers 8 square feet at 3 inches deep, or 12 square feet at 2 inches deep. This calculator handles those conversions plus the bagged-versus-bulk break-even point so you don't overpay for either.
Enter your bed dimensions and target depth. The calculator returns total cubic yards, total bags (assuming 2 cubic foot bags from Home Depot or Lowe's), and a recommendation on whether to buy bagged or order bulk.
The break-even is around 2 cubic yards. Below that, bagged usually wins. Above 2 yards, bulk delivery saves real money, sometimes 60% per cubic yard.
How to use it
How to use this calculator
- Measure your bed in feet. Use the longest and widest dimensions for irregular shapes. The calculator's safety margin handles the rounding.
- Pick your target depth: 2 inches for established beds, 3 inches for new beds with weed suppression, 4 inches for slope stabilization.
- The calculator returns cubic yards, bag count, and a bagged-vs-bulk recommendation.
- For multiple beds, calculate each separately and add them up.
- If you're under 1 cubic yard, bagged is almost always the right call.
Mulch settles 10–15%. Topsoil compacts more, bump to 15%.
| Bed size | Cubic feet | Cubic yards | 2 ft³ bags |
|---|---|---|---|
| 10 × 10 | 25.0 | 0.93 | 13 |
| 12 × 12 | 36.0 | 1.33 | 18 |
| 15 × 15 | 56.3 | 2.08 | 29 |
| 20 × 20 | 100.0 | 3.70 | 50 |
| 25 × 30 | 187.5 | 6.94 | 94 |
Reading the output
Understanding your result
The big number is total bags of 2-cubic-foot mulch. The cubic yard figure tells you whether to switch to bulk delivery, the break-even is around 1.5 to 2 cubic yards.
What the bag count assumes: 10% settle factor and standard 2-cubic-foot bag size from Home Depot or Lowe's. If you're buying 3-cubic-foot bags from a landscape supply yard, the bag count drops by a third.
When to bump the depth higher: first season for a new bed where you want strong weed suppression, slopes where mulch slides downhill, or any area with heavy summer sun where mulch dries out fast. Going from 2 to 3 inches adds 50% to your material cost, so the math matters.
When to round up vs round down: always round up. Mulch settles 10 to 15% in the first month, and most beds end up looking thin if you under-buy. An extra bag at $5 is cheaper than a return trip.
If the result crosses 2 cubic yards, the bulk recommendation kicks in. Bulk mulch from a local yard is typically $30 to $55 per cubic yard plus a $50 to $90 delivery fee. Above 2 yards, that math beats bagged retail by a wide margin.
Common mistakes (and how to avoid them)
✗ Measuring with averaged dimensions.
Fix: Use the longest and widest points of an irregular bed, not eye-averaged numbers. The calculator handles the safety margin.
✗ Forgetting the depth in your math.
Fix: A 2-inch layer needs 2/3 the volume of a 3-inch layer. Decide on depth first, calculate second.
✗ Going thinner than 2 inches.
Fix: Below 2 inches, the mulch doesn't suppress weeds or hold moisture. You'll be re-mulching by midsummer.
✗ Going thicker than 4 inches.
Fix: Mulch deeper than 4 inches can starve plant roots and create water-shedding mats. More is not better past a point.
✗ Ordering bulk for a small project to 'save money.'
Fix: The delivery fee and minimum order erase the savings on anything under 2 cubic yards.
Frequently asked questions
How many bags of mulch in a cubic yard?
How deep should I apply mulch?
When is the break-even between bagged and bulk?
Does mulch type matter for the calculator?
How often should I replace mulch?
Tools you may need
Most homeowners already have a rake and gloves. Borrow or rent the rest before buying.
- Steel rake. For spreading and leveling. A bow rake works for both mulch and topsoil.
- Wheelbarrow. A 6 cu ft contractor model moves about 3 bags at a time without tipping.
- Work gloves. Mulch is rough on hands and dyed mulch can stain, leather or coated nitrile both work.
- Edging tool or half-moon edger. Cut a clean bed edge before you spread, or the mulch will creep onto the lawn.
- Landscape fabric. Optional. Useful under decorative stone; skip it under mulch, it traps moisture and degrades fast.
Related guides
Where to buy your materials
We've linked to common products at Home Depot and Lowe's below. These are affiliate links, meaning we earn a small commission if you buy through them, at no cost to you. We've used these specific products on projects ourselves. If your local independent yard has a better price, take it.
Bagged mulch
×22Mulch · 2 ft³ bags. Compare both, local stock and color choices vary.
Affiliate links, same price for you, helps keep the calculators free.
Cost: bagged vs bulk
Material-only ranges based on typical US retail and landscape-supply pricing. Bulk includes a short delivery fee.
At this size, bulk usually wins on price even after the delivery fee.
Local pricing · Miami-Dade & Broward
Get local bulk mulch pricing
At 1.63 yd³, local yards almost always beat bagged retail once you factor in the per-yard price and a single delivery fee. We're starting MaterialMath's local supplier coverage in Miami-Dade and Broward first, send your numbers and we'll help you compare 2–3 yard quotes.
- Compare price per yard, delivery fee, and minimum order across yards.
- Ask about color and grade (dyed vs. natural, hardwood vs. cypress).
- Confirm truck access and where they'll dump the pile.
Outside South Florida? Search "landscape supply near me" and ask the same questions, more regions coming soon.
Want a printable version?
We'll email a one-page PDF summary of this page's math plus a calling script for local supply yards. Everything we know is right here on the page, the PDF just makes it portable.
One email with your file. Unsubscribe in one click. No newsletter.