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Blueprint Calc

Mulch Calculator

Enter bed size and depth — get cubic yards, number of 2 cu ft bags, and whether bulk delivery beats bagged for your job. Supports rectangles, circles, and custom areas.

How much mulch do I need?

Measurements in feet. Default is a 20 x 4 ft border at 3 in depth.

You need
  • Mulch volume
    0.74 cu yd
    20.00 cu ft of coverage
  • Bags needed
    10 × 2 cu ft bags
    at 2 cu ft per bag
  • Coverage area
    80.00 sq ft
    at 3" depth
  • Bagged cost
    ~$45
    10 bags × $4.50

What you'll need to buy

Prices approximate · Links go to retailer search results
Estimated total: ~$67 (materials, before tax)

Product links go to Home Depot search results — pick the best match for your project. Prices shown are rough averages.

How we calculated it

Mulch is a volume problem, not an area problem. Here is the math this calculator uses:

  1. Area in square feet = length × width (rectangle) or π × radius² (circle)
  2. Volume in cubic feet = area × (depth in inches / 12)
  3. Cubic yards = cubic feet ÷ 27 (1 yard = 27 cu ft)
  4. Bag count = cubic feet ÷ 2 (standard Home Depot / Lowe's 2 cu ft bag), rounded up

Bulk mulch is typically priced per cubic yard delivered. Once you need more than 2 yards (about 27 bags), bulk is usually cheaper — even after a $50-100 delivery fee. The calculator flags that threshold.

Depth recommendation: 2-4 inches is industry standard. Less than 2 washes out and lets weeds through. More than 4 can suffocate shallow-rooted plants and hold moisture against stems.

Mulch quantities by bed size (3 in depth)

Cubic yards and 2 cu ft bag count for common bed dimensions, assuming the sweet-spot 3 inch depth.

Bed size Area Volume Cubic yards 2 cu ft bags
4 × 8 ft 32 sq ft 8 cu ft 0.30 yd 4
4 × 12 ft 48 sq ft 12 cu ft 0.44 yd 6
4 × 20 ft 80 sq ft 20 cu ft 0.74 yd 10
10 × 10 ft 100 sq ft 25 cu ft 0.93 yd 13
10 × 20 ft 200 sq ft 50 cu ft 1.85 yd 25
20 × 20 ft 400 sq ft 100 cu ft 3.70 yd 50
30 × 40 ft 1,200 sq ft 300 cu ft 11.1 yd 150

Rule of thumb: 1 cubic yard covers 108 sq ft at 3 inches. Bulk delivery beats bagged above ~3 yards in most markets.

How depth affects mulch volume

Mulch needed per 100 sq ft of bed, by depth.

Depth Volume Cubic yards 2 cu ft bags
1" 8.3 cu ft 0.31 yd 5
2" 16.7 cu ft 0.62 yd 9
3" 25 cu ft 0.93 yd 13
4" 33.3 cu ft 1.23 yd 17
5" 41.7 cu ft 1.54 yd 21
6" 50 cu ft 1.85 yd 25

3 inches is the recommended sweet spot: deep enough for weed suppression, shallow enough not to suffocate roots.

Frequently asked questions

How many bags of mulch in a yard?
One cubic yard equals 27 cubic feet. At 2 cubic feet per bag (the standard Home Depot / Lowe's size), you need 13.5 bags to make a yard. Buying bulk is usually cheaper once you need more than 2 yards.
How much mulch do I need for a 100 sq ft bed?
At a recommended 3" depth, 100 sq ft needs 25 cubic feet of mulch — that is about 13 × 2 cu ft bags or just under one cubic yard. At 2" depth you would need 17 cubic feet (9 bags).
How deep should mulch be?
2 to 4 inches is the sweet spot. Less than 2 inches lets weeds punch through and washes out in rain. More than 4 inches can suffocate plant roots and keep the soil too wet. 3 inches is what this calculator defaults to.
Is bagged or bulk mulch cheaper?
Bulk is usually 30-50% cheaper per cubic yard once you need more than 2 yards, but you pay a delivery fee ($50-100 typical). For small beds (under 10 bags), bagged is easier and the delivery cost does not justify bulk. Run both numbers before deciding.
How often should mulch be replaced?
Once a year is normal — most mulch loses color and compacts by ~50% over 12 months. Budget replacements every spring. Rubber and stone mulch last much longer (5+ years) but they cost more upfront and do not feed the soil.
What kind of mulch is best?
Hardwood mulch is the cheapest and fine for most beds. Cedar and cypress resist decay and insects (slightly more expensive). Pine bark is acidic — good for azaleas, rhododendrons, and blueberries. Dyed mulches are mostly aesthetic; the color fades in 3-6 months.
How much does a yard of mulch weigh?
About 400-800 lbs when dry, 1,000-1,500 lbs when wet. Most half-ton pickups can carry one yard safely. Bigger loads need a full-size truck or delivery.
Should I put down landscape fabric before mulching?
Only for paths, around decorative rock, or under playground mulch. In planting beds, fabric blocks organic matter from reaching the soil and tangles with root systems over time. A 3 inch mulch layer alone suppresses most weeds.
Can I mulch over grass or weeds?
Small weeds — yes, if you put down 4+ inches. Grass — no, it will grow through. Kill the grass first (cardboard + 2-3 weeks, or glyphosate) before laying mulch, or you will be pulling crabgrass through your beds all summer.
When is the best time to mulch?
Late spring, after the soil has warmed. Mulching too early (while soil is still cold) delays spring growth. A second top-up in early fall adds winter insulation for shallow-rooted perennials.

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