How to Calculate How Much Gravel You Need

The formula

cubic yards = (length ft × width ft × depth in ÷ 12) ÷ 27
tons        = cubic yards × density (1.35 – 1.5)
order       = tons × 1.10   (10% waste allowance)

Worked example: a rectangular driveway

A 60 ft by 12 ft driveway, resurfacing at 3 inches with #57 stone.

1. Area: 60 × 12 = 720 sq ft
2. Depth in feet: 3 ÷ 12 = 0.25 ft
3. Cubic feet: 720 × 0.25 = 180 ft³
4. Cubic yards: 180 ÷ 27 = 6.67 yd³
5. Tons: 6.67 × 1.4 = 9.33 tons
6. With 10% waste: 9.33 × 1.10 = 10.3 tons

One tandem-axle load (12 tons) covers it with room to spare. Check against the gravel calculator.

Worked example: a circular patio

A 14 ft diameter fire pit surround at 3 inches of pea gravel.

1. Radius: 14 ÷ 2 = 7 ft
2. Area: π × 7² = 3.1416 × 49 = 154 sq ft
3. Cubic feet: 154 × 0.25 = 38.5 ft³
4. Cubic yards: 38.5 ÷ 27 = 1.43 yd³
5. Tons: 1.43 × 1.35 = 1.93 tons
6. With 10%: 2.12 tons

Worked example: a multi-layer driveway

A new build is three separate calculations, because each layer is a different stone at a different depth. Same 720 sq ft driveway:

That is four tandem loads. The driveway calculator runs all three layers in one step.

Irregular shapes

Break the area into pieces you can calculate, then add them:

• Rectangle: length × width
• Triangle: (base × height) ÷ 2
• Circle: π × radius²
• Half circle: (π × radius²) ÷ 2
• Curved driveway: centreline length × width

Measuring a curve along its centreline rather than an edge is what makes it accurate — the outside edge overstates the area and the inside understates it. The circular driveway calculator handles this.

The two mistakes that cause short orders

1. Forgetting the waste allowance

The arithmetic is right, but it was done on the finished depth. Gravel compacts and settles, and some always disappears into the subgrade. Order 10% over.

2. Dividing by 12 in the wrong place

Depth is in inches and everything else is in feet. Converting depth to feet before multiplying is the step people skip, and it produces an answer twelve times too large.

Sanity checks

• One cubic yard of gravel weighs about 1.4 tons, or 2,800 lb.
• One ton covers about 100 sq ft at 2 inches deep.
• One cubic yard covers about 100 sq ft at 3 inches deep.
• A tandem dump truck carries about 12 tons, or 8 to 10 cubic yards.

If your answer is wildly off one of these, check where the 12 and the 27 went.