Concrete Pad Calculator

This concrete pad calculator is built for a specific type of pour: a flat rectangular slab used as a patio, shed foundation, parking pad, or equipment base. As a concrete calculator for patio projects and a shed foundation concrete calculator in one, there's no shape selector — just length, width, and thickness. If you know what you're building and it's a rectangle, this is the fastest way to get from dimensions to bag count. Enter your measurements, hit calculate, and you have exactly what you need to order.

How to Use the Concrete Pad Calculator

• Measure your pad's length and width in feet.
• Enter the desired thickness in inches — 4 inches is standard for patios and shed foundations, 6 inches for parking pads.
• Click "Calculate Pad" to get cubic feet, cubic yards, and bag counts.
• Order 10% more than the calculated amount to account for waste and spillage.

Concrete Pad Example: 12×16 Patio at 4 Inches

A 12-foot by 16-foot patio slab poured at 4 inches thick:

At 2.37 cubic yards, a small readymix truck delivery is more practical than mixing 107–143 individual bags. Most suppliers have a 1-yard minimum — call ahead to confirm availability and short-load fees. For a larger pour — how many yards of concrete for a 20×20 pad, for example — the answer at 4 inches is 4.94 cubic yards, well into readymix territory.

Concrete Pad Thickness Guide

4 inches — standard for patios, walkways, and shed foundations. Adequate for foot traffic and light loads, works with typical residential soil conditions.

6 inches — recommended for parking pads and equipment bases where vehicle or machine weight is a factor. A 6-inch pad uses 50% more concrete than a 4-inch pad of the same dimensions.

3.5 inches — minimum for residential use, sometimes used to reduce material cost. Not recommended where freeze-thaw cycles are a concern. Use this concrete pad thickness calculator to compare volumes at different depths before committing to your order.

Frequently Asked Questions

How thick should a concrete pad be?

For patios and shed foundations, 4 inches is the standard minimum. Equipment pads and parking pads should be 6 inches to handle vehicle weight without cracking. In freeze-thaw climates, thicker pads are more durable — the deeper the slab, the less it is affected by ground movement from frost heave. Going from 4 to 6 inches on a 12×16 pad adds exactly 1.19 cubic yards to your order.

How much concrete do I need for a 12x12 patio?

A 12×12 patio at 4 inches thick requires 48 cubic feet, or 1.78 cubic yards — about 107 60lb bags or 80 80lb bags. This sits in the awkward zone where bags are a lot of work but you're only ordering 1.78 yards of readymix. Factor in your local short-load fee before deciding which route makes more sense for your budget and timeline.

How much concrete do I need for a shed foundation?

A 10×12 shed foundation at 4 inches thick needs 40 cubic feet — 1.48 cubic yards, or about 89 60lb bags. A 12×16 foundation at 4 inches needs 64 cubic feet — 2.37 cubic yards, or about 143 60lb bags. Both are solid readymix candidates. If you're DIYing a shed on a tight budget, bags work but plan for a full day of mixing for the larger size.

How do I calculate concrete for a concrete patio?

The formula is: cubic feet = length × width × (thickness ÷ 12). A 16×20 patio at 4 inches: 16 × 20 × 0.333 = 106.67 cubic feet, divided by 27 = 3.95 cubic yards. Order at least 4.35 cubic yards with 10% overage. This pad calculator does all that automatically — just enter the three numbers.

Can I pour a concrete pad in sections?

Yes, large pads are commonly poured in sections with control joints cut between them. Sections should be roughly square and no larger than about 10×10 for a 4-inch pad. Pouring in sections lets you manage volume per session, which matters when mixing bags by hand. Use this calculator for each individual section's dimensions and add up the totals to get your overall material order.