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 actual formed length and width in feet.
- Enter slab thickness in inches, then handle thickened edges or footings as separate estimates.
- Break irregular slabs into rectangles so the volume calculation stays transparent.
Common mistakes
- Using square feet without converting thickness into volume.
- Missing thickened edges, turndowns, steps, or separate pads.
- Ordering exactly the calculated amount with no allowance for site variation.
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): 1.3 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 Wheelchair Ramp Landing Concrete Pad Calculator result to plan materials.
Before you buy materials
- Compare cubic yards, cubic feet, and bag counts before deciding between ready-mix and bags.
- Confirm final slab details with plans, product labels, or a qualified professional when accuracy matters.
FAQ
What is the example wheelchair ramp landing 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 1.3 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.