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Concrete pad calculator

Pads are slabs with a job: hold a condenser, a generator, or a shed. The math is the same family as a patio slab — length × width × thickness — but the shopping story is smaller pours, often bagged, with waste for over-excavate. Use this when you do not need footings/holes modes. For a full shape toolkit, stay on the concrete calculator. For a big patio, the slab calculator is the clearer search match.

ft
ft
in
10%
0510152025

+10% so you don't come up short

ORDER ESTIMATESlab
Cubic yards1.36
80 lb bags62
Waste applied10%
How it calculates
L × W × (T ÷ 12) → cu ft; ÷ 27 → yd³; × (1 + 10% waste); bags = ceil(order cu ft ÷ 80 lb yield).

Estimate only — not a contractor bid. Confirm bag yields and local codes before you pour or order.

When to use

AC condenser pad; generator pad; small shed pad shopping list; bag vs mini-mix decision under one yard.

When not to

Structural house footings — drawings. Hot tub pads with point loads — manufacturer pad specs. Driveways — use slab or asphalt pages.

Assumptions

Rectangular pad. Thickness default 4 in (editable). Bag yields same as batch 1 concrete (80 lb ≈ 0.60 cu ft, etc.). Waste default 10%.

Worked examples

Example 1

3×3 ft AC pad, 4 in, waste 10%, 80 lb bags
→ ≈ 0.11 yd³ ordered → about 5–6 bags of 80 lb

Many precast pads exist — compare bagged pour vs buying precast.

Example 2

8×10 shed pad, 4 in, waste 10%
→ ≈ 1.09 yd³ ordered — often still bag or short-load territory depending on access

How it calculates

Same as slab: dimensions to cubic yards, waste, then bags by yield.

  1. Enter pad length, width, and thickness in inches.
  2. Pick 40 / 60 / 80 lb bags and set waste.
  3. Read ordered yards and bag count on the ticket.
cu ft = L × W × (T ÷ 12)
yd³ = cu ft ÷ 27
order = volume × (1 + waste%)
bags = ceil(order cu ft ÷ yield_per_bag)

Common traps

  1. Manufacturer pad size may beat your guess — check the unit clearances.
  2. Base gravel under the pad is a separate gravel line.
  3. Thickness in inches — same trap as every concrete page.
  4. Level and drainage — volume math does not slope the pad for you.

Next tool

Multi-shape pours → concrete calculator.

Larger patio/drive → concrete slab calculator.

Bags from a known yardage → concrete bag calculator.

FAQ

L × W × thickness → yards/bags; many pads are ~3×3 or per manufacturer.

Related

Estimate only — not a contractor bid or engineered takeoff. Confirm bag yields and local codes before you pour or order.