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Square Feet to Cubic Yards Calculator

Ready to calculate
ft² × depth ÷ 27.
Bags Included.
ft³ · yd³ · m³.
100% Free.
Privacy Secure.

How it Works

01Enter Area

Type square footage of the area — driveway, garden bed, slab, mulch bed.

02Add Depth

How deep in inches — 4 in slab, 6 in base, 2 in mulch, 3 in gravel.

03Divide by 27

Cubic feet ÷ 27 = cubic yards. Industry-standard conversion.

04Bags Priced

Also outputs 60/80 lb concrete bags and 2/3 cu-ft mulch bags.

What is a Square Feet to Cubic Yards Calculator?

A square feet to cubic yards calculator — also called a sq ft to cu yd converter, area-to-volume calculator, or concrete yard estimator — converts a flat area (ft²) plus a depth into a volume (yd³) in one step. Every landscaping, concrete, mulch, gravel, topsoil, and hardscape project starts the same way: you measure the area, decide on a depth, then need to know how much material to order. Too low and you run out mid-job and stop work; too high and you've got half a pallet of concrete or six extra yards of mulch rotting on the driveway.

This tool uses the precise formula ft² × (depth_in / 12) / 27 = yd³ — where 27 ft³ = 1 yd³ exactly, and the /12 converts depth from inches (the unit hardware stores and engineers actually use) to feet (the unit square footage is measured in). It also outputs concrete bag counts for both 60 lb bags (0.45 ft³ yield) and 80 lb bags (0.60 ft³ yield), plus mulch bag counts for 2 and 3 cubic-foot bagged mulch sizes — so you know exactly what to buy before you leave the house.

Great for concrete slabs (4 inch typical), gravel driveways (3-4 inch top coat, 6 inch base), mulch beds (2-3 inch for annual beds, 3-4 inch for perennial), pea gravel paths (2 inch), decorative river rock (3-4 inch), topsoil (3-6 inch for lawn repair, 12-18 inch for raised beds), sand leveler under pavers (1-2 inch), and any flat-area spread or pour.

The tool also outputs cubic feet, cubic yards, and cubic meters simultaneously — covering US contractors (yd³), metric engineers (m³), and bagged-material buyers (ft³). No waste factor is baked in by default, so add 5-10% yourself when ordering — landscape crews routinely short an order by exactly the amount they skimped on waste.

Perfect for DIY homeowners scoping concrete slabs, gravel driveways, and mulch beds before a hardware store trip; landscapers quoting topsoil, mulch, and decorative rock jobs; concrete contractors double-checking customer dimensions before ordering ready-mix; and garden designers sizing raised-bed soil orders.

How It Works

Area input — square footage of the spread area. Works for any rectangle, or add up multiple rectangles for L-shaped beds.
Depth input — inches. Typical depths: 4 in concrete slab, 2 in mulch, 3 in gravel driveway top, 6 in gravel base, 1-2 in sand leveler.
Convert — depth_in / 12 gives depth in feet, then ft² × depth_ft = ft³ total volume, then ÷ 27 for yd³.
Bag outputs — divides volume by bag yield: 80 lb concrete = 0.6 ft³/bag, 60 lb = 0.45 ft³/bag, mulch bags = their cubic-foot rating.
No rounding loss — internal math uses full precision; only the displayed numbers are rounded to avoid cumulative error.

Conversion Formula

Three lines to go from flat area to ordered material:

Volume_ft³ = Area_ft² × (Depth_in / 12)
Volume_yd³ = Volume_ft³ / 27
Volume_m³ = Volume_ft³ × 0.0283168
Concrete 80 lb bags = ceil(Volume_ft³ / 0.6)
Concrete 60 lb bags = ceil(Volume_ft³ / 0.45)
Mulch 2 cu-ft bags = ceil(Volume_ft³ / 2)
Mulch 3 cu-ft bags = ceil(Volume_ft³ / 3)

The ÷ 27 step is non-negotiable — one cubic yard is exactly 3 × 3 × 3 = 27 cubic feet. Ready-mix concrete, topsoil, gravel, and mulch in bulk are all sold by the cubic yard.

Real-World Example

Worked Example

A 20 ft × 15 ft concrete patio at 4 inches thick:

  • Area = 20 × 15 = 300 ft²
  • Depth in ft = 4 / 12 = 0.333 ft
  • Volume ft³ = 300 × 0.333 = 100 ft³
  • Volume yd³ = 100 / 27 = 3.7 yd³
  • 80 lb concrete bags = ceil(100 / 0.6) = 167 bags
  • At a concrete yard: order 4 yd³ (rounded up). $150/yd × 4 = $600 + delivery. Versus bags: 167 × $6.50 = $1,086. Ready-mix wins at this size.

Who Uses This Calculator?

1
DIY homeowners scoping concrete slabs, gravel driveways, and mulch beds before a hardware store trip
2
Landscapers quoting topsoil, mulch, and decorative rock jobs
3
Concrete contractors double-checking customer dimensions before ordering ready-mix
4
Garden designers sizing raised-bed soil orders and path material
5
Construction estimators converting square-footage site plans to truck-load quantities

Technical Reference

ASTM C33 — standard specification for concrete aggregates. Bag yields (0.6 ft³ per 80 lb, 0.45 ft³ per 60 lb) are derived from typical aggregate-to-water-to-cement ratios.

Cubic yard definition — 27 ft³ exactly (3 ft × 3 ft × 3 ft). Used for all US concrete and aggregate bulk delivery.

Key Takeaways

The formula is deceptively simple but easy to botch by hand — most estimation errors come from mixing inches and feet in the same calculation. Keep depth in inches, divide by 12 first, then multiply by area, then divide by 27. Add 5-10% waste for any outdoor spread (wind redistribution, compaction settling, uneven subgrade): landscape crews who skip this step end up 6-10% short on every order. For flat concrete slabs over 2 cubic yards, ready-mix delivery always beats bagged on cost; under 1 cubic yard, bags usually win. The crossover is around 1.2-1.5 yd³ depending on local delivery fees and short-load surcharges. This calculator gives both counts so you can see the economic crossover directly and pick the cheaper option.

Frequently Asked Questions

How do you convert square feet to cubic yards?
Multiply square feet by depth in inches, divide by 12, then divide by 27. So 100 ft² × 4 in / 12 / 27 = 1.23 cubic yards.
How many cubic yards in 100 square feet?
Depends on the depth. At 4 in thickness: 1.23 yd³. At 6 in: 1.85 yd³. At 2 in (for mulch): 0.62 yd³. Always multiply area by depth (as feet) and divide by 27.
How many square feet in a cubic yard?
Depends on depth. 1 yd³ covers 108 ft² at 3 in deep, 81 ft² at 4 in deep, 54 ft² at 6 in deep. The ratio is 27 ÷ (depth_in / 12) = 324 / depth_in ft².
How many cubic yards of concrete for a 20×20 slab?
400 ft² × 4 in / 12 / 27 = 4.94 yd³ for a 4 inch slab. Order 5 yd³ to account for waste. At $150/yd³, material cost is about $750.
How many 80 lb bags of concrete in a cubic yard?
45 × 80 lb bags per cubic yard (1 bag yields 0.6 ft³, and 27 ft³ / 0.6 = 45). For 60 lb bags, about 60 bags per yard.
How many yards of mulch do I need for 1,000 square feet?
At 2 inches deep: 1,000 × 2 / 12 / 27 = 6.17 yd³. At 3 inches deep: 9.26 yd³. Mulch compresses, so order the higher depth if you want a full layer.
What is the difference between square feet and cubic yards?
Square feet measures area (a flat surface). Cubic yards measures volume (area × depth). You cannot convert one to the other without knowing the depth.
How do I calculate cubic yards of gravel?
Same formula: area in ft² × depth in inches / 12 / 27. For a gravel driveway: typically 3 in top coat + 6 in base = 9 in total depth. 300 ft² × 9 / 12 / 27 = 8.33 yd³ total.
Can I convert cubic yards to cubic feet?
Yes. 1 yd³ = 27 ft³ exactly. To go from yd³ to ft³, multiply by 27. Ready-mix is sold by yd³, bagged concrete by ft³ (yields).
How much does 1 cubic yard of concrete cost?
US average for ready-mix: $130-$180 per cubic yard delivered, depending on region, PSI spec, and delivery distance. Most suppliers have a 1-yard minimum and short-load fees for anything under 3 yards.

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The ToolsACE Team

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Disclaimer

Educational reference. Always add 5-10% waste when ordering. For structural pours, verify with your concrete supplier.