Estimate concrete, base, reinforcement, joints, cost, and pour-day conditions for a patio, shed pad, or slab.
Enter slab length, width, and thickness to calculate design volume and a recommended order quantity with waste. The Slab / Pad project includes quick presets for patios, shed pads, grill pads, hot-tub pads, and general rectangular slabs. The planner also estimates bag counts, ready-mix loads, compacted and loose base material, reinforcement, form lumber, control-joint spacing, saw-cut depth, and a rough material cost range. Switch between US and metric units at any time.
Start with the actual finished dimensions, then choose a quick preset or enter a custom size. Base depth and reinforcement are planning inputs, not structural design. The calculator’s joint plan caps spacing to the slab footprint and estimates saw cuts at about one-quarter of slab thickness. Irregular edges, thickened sections, slopes, drains, and embedded items should be measured separately or covered by an adjusted waste allowance.
For larger pours, compare the ready-mix recommendation with bag quantities and confirm the final order with the supplier. Local soil, frost, drainage, load, and code requirements can change the appropriate slab section. The weather step uses National Weather Service forecast data when a US ZIP code and pour date are available.
Slab volume is length × width × thickness. In US units, thickness is divided by 12 to convert inches to feet, cubic feet are divided by 27 for cubic yards, and the chosen waste factor is applied to the recommended order.
The included patio preset starts at 4 inches, but required thickness depends on loads, support, exposure, and local requirements. Vehicle, hot-tub, lift, and other concentrated loads need project-specific verification.