Bag Calculator

Find out how many bags of mulch, soil, gravel, or sand you need to fill an area, plus the total volume in cubic feet and cubic yards and the estimated cost.

Quick Facts

Formula
Volume = Length × Width × (Depth ÷ 12)
Depth is entered in inches and converted to feet before multiplying, giving cubic feet.
Cubic yard
1 cubic yard = 27 cubic feet
Bulk suppliers typically sell mulch, soil, and gravel by the cubic yard rather than the bag.
Rounding
Bags needed is rounded up
Rounding up avoids running short mid-project; leftover bags can be used on a future job.

Your Results

Calculated
Volume needed
-
Length × width × depth, in cubic feet
Volume (cubic yards)
-
1 yd³ = 27 ft³
Bags needed
-
Rounded up to whole bags
Estimated cost
-
Bags needed × price per bag

Ready

Enter your area, depth, and bag size, then press Calculate.

About the Bag Calculator

This calculator figures out how many bags of loose material — mulch, topsoil, garden soil, sand, or gravel — you need to cover a rectangular area to a given depth. It uses the standard volume formula for a rectangular prism (length × width × height), then divides that volume by how much material comes in a single bag.

The formula

Volume needed in cubic feet is Length (ft) × Width (ft) × Depth (ft), where depth in feet equals the depth in inches divided by 12. That figure is converted to cubic yards by dividing by 27, since one cubic yard is a 3 ft × 3 ft × 3 ft cube (27 cubic feet). The number of bags is the volume in cubic feet divided by the bag's coverage in cubic feet, rounded up to the next whole bag, and the estimated cost is bags needed multiplied by the price per bag.

How to get the best results

  • Measure length and width at the widest points of the area, and round irregular shapes up to the nearest rectangle that contains them.
  • Pick a realistic depth: about 2–3 inches for mulch top-dressing, 4–6 inches for a new garden bed, and deeper for structural fill or a raised bed.
  • Check the coverage volume printed on your actual bag — it varies by brand and material even when bags look similar in size.
  • For large areas, compare the bagged total this tool gives you to a bulk (by-the-cubic-yard) delivery quote from a local supplier.

Practical context

This calculator assumes a uniform depth across a flat rectangular area and doesn't account for compaction, slopes, or spillage. Add extra material for irregular shapes or uneven ground, and always round up to a whole bag — buying one extra bag is far cheaper than running short mid-project and making a second trip.

Frequently Asked Questions

How do I calculate how many bags I need?
Multiply the area's length and width in feet to get square footage, multiply that by the depth in feet (depth in inches divided by 12) to get cubic feet, then divide by the cubic feet in one bag and round up. For example, a 10 ft × 10 ft bed at 3 inches deep needs 10 × 10 × 0.25 = 25 cubic feet, or 34 bags at 0.75 cubic feet each.
How many cubic feet are in a cubic yard?
One cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft). Bulk suppliers usually sell mulch, soil, and gravel by the cubic yard, while home-improvement stores sell smaller bagged quantities, commonly 0.5 to 3 cubic feet per bag.
Should I round the number of bags up or down?
Always round up to the next whole bag. Rounding down leaves you short of material partway through the job, and running out mid-project usually costs more time than buying one extra bag up front.
Is bagged or bulk material cheaper?
It depends on the volume and local pricing, but bagged material generally costs more per cubic foot than bulk delivery once a project needs more than roughly 2–3 cubic yards. For small areas, bags are usually more convenient; for large areas, ask a supplier for a bulk price per cubic yard and compare it with the bag total this calculator gives you.

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