How much rebar do I need?
A basic rebar grid estimate uses slab or footing dimensions, bar spacing, bar length, and waste. The calculator estimates count for a simple rectangular layout.
Spacing, laps, and waste
Closer spacing increases bar count. Lap lengths, bends, chairs, hooks, edge offsets, and cuts can change the real order and should be planned separately.
Rebar quantity is not reinforcement design
This calculator is a material planner. Required bar size, spacing, cover, laps, and layout depend on plans, loads, and local requirements.
Common concrete slab sizes
Cubic yards below are before waste. Add your project waste percentage before ordering.
| Slab size | 4 in thick | 5 in thick | 6 in thick |
|---|---|---|---|
| 10 ft x 10 ft | 1.23 cu yd | 1.54 cu yd | 1.85 cu yd |
| 10 ft x 12 ft | 1.48 cu yd | 1.85 cu yd | 2.22 cu yd |
| 12 ft x 12 ft | 1.78 cu yd | 2.22 cu yd | 2.67 cu yd |
| 20 ft x 20 ft | 4.94 cu yd | 6.17 cu yd | 7.41 cu yd |
| 24 ft x 24 ft | 7.11 cu yd | 8.89 cu yd | 10.67 cu yd |
| 30 ft x 40 ft | 14.81 cu yd | 18.52 cu yd | 22.22 cu yd |
Before you calculate
- Measure the patio length and width in feet, then enter the planned slab thickness in inches.
- Split L-shaped patios, steps, or widened seating areas into separate rectangles.
- Keep waste visible because patio edges, forms, and base variation can change the final order.
Common mistakes
- Using patio square footage alone without including slab thickness.
- Forgetting thickened edges, steps, curves, or separate landing areas.
- Comparing a concrete-only estimate with a full installed patio quote.
Formula
cubic yards = (length * width * (thickness / 12) / 27) * (1 + wastePercent / 100)
Assumptions
- Concrete quantity is a planning estimate, not structural design.
- Thickness, forms, subgrade, reinforcement, drainage, slopes, and local requirements should be checked separately.
- Round ready-mix, bags, forms, sealers, and accessories up before ordering.
Example
Estimated concrete needed (cubic yards): 0.98 cubic yards
How to use this calculator
- Enter length in ft.
- Enter width in ft.
- Enter thickness in in.
- Enter waste in %.
- Review the live estimate and compare it with the example result.
- Check the formula, assumptions, product labels, and site conditions before using the Patio Setup Chair Cover Rail Concrete Pad Calculator result to plan materials.
Before you buy materials
- Use the cubic-yard result when discussing ready-mix minimums or bagged concrete alternatives.
- Confirm base, slope, reinforcement, finish, and local requirements before scheduling a pour.
FAQ
What is the example patio setup chair cover rail concrete pad cubic-yard result?
Use length, width, thickness or depth, and waste, then calculate the planning result. In the default example, the result is 0.98 cubic yards.
How do I calculate rebar for a slab?
Estimate bars in each direction from slab dimensions and spacing, then account for bar length, laps, cuts, and waste.
Does this include lap length?
No. Add lap lengths and cut waste separately based on your plans or qualified guidance.
Can this choose rebar size or spacing?
No. It estimates quantity from the spacing you enter; it does not design reinforcement.
Should I include chairs, ties, or mesh?
Those materials are not included in the rebar count. Plan them separately.
Related calculators
This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.