Understanding This Calculator
Reinforcing a slab or wall with a rebar grid means running bars in both directions at a set spacing, tied together where they cross. Getting the count right matters both for structural integrity — too wide a spacing under-reinforces the concrete — and for your budget, since rebar is sold and priced by the stick or by weight. This calculator lays out a two-way grid across your slab dimensions and gives you sticks, linear footage, and total weight.
Rebar comes in standard 20 ft stock lengths from most suppliers, so this tool rounds your total linear footage up to whole sticks. Weight is calculated from the standard weight-per-foot for each bar size, which is useful for costing since rebar is frequently quoted by the pound or by the ton for larger jobs.
- L, W slab length and width (ft)
- s bar spacing (inches)
- lb/ft weight per foot for the selected bar size
| Bar Size | Diameter (in) | Weight (lb/ft) |
|---|---|---|
| #3 | 0.375 | 0.376 |
| #4 | 0.500 | 0.668 |
| #5 | 0.625 | 1.043 |
| #6 | 0.750 | 1.502 |
Frequently Asked Questions
Why does the calculator add 1 to the bar count?
A grid needs a bar at both edges as well as every spacing interval in between, so the count is always one more than the number of spacing gaps across the dimension — this matches standard rebar layout practice.
Does this account for overlap splices between rebar sticks?
No — this gives raw linear footage and stick count for the grid as laid out. If a run exceeds a single 20 ft stick and needs a lap splice, add roughly 12-18 inches of overlap per splice to your material order.