Rebar takeoff calculator.
Type in your slab and footing dimensions, pick a bar size and spacing. Get the bar count, linear feet, weight in tons, stock pieces, laps, tie wire and chairs — and download it as a proper Excel takeoff template with live formulas.
Lap + waste % covers 40-bar-diameter splices and cut waste.
| Element | Length (ft) | Width (ft) | Bar size | Spacing (in) each way | Mats | Element LF |
|---|
| Material | Qty | Unit | How it’s figured |
|---|
How the math works
Every factor in this calculator is a standard estimating rule of thumb, and every one of them is visible in the Excel download so you can audit or adjust it. Each element is treated as a flat rectangular grid reinforced both ways:
- Bars running lengthwise — width × 12 ÷ spacing, rounded up, plus one closing bar. Each runs the full length.
- Bars running widthwise — length × 12 ÷ spacing, rounded up, plus one closing bar. Each runs the full width.
- Element linear feet — mats × (lengthwise bars × length + widthwise bars × width).
- Lap + waste — total LF × (1 + lap %). The default 15% covers typical 40-bar-diameter splices and cut waste.
- Weight — LF with laps × the bar’s unit weight, then pounds ÷ 2,000 for tons.
- Stock pieces — LF with laps ÷ your stock bar length (20/30/40/60 ft), rounded up, per bar size.
- Tie wire — ≈16 lb per ton of rebar, ordered in 3.5-lb rolls.
- Bar chairs / supports — one per 9 SF of mat area, per mat.
Bar unit weights used (lb per foot):
| Bar | #3 | #4 | #5 | #6 | #7 | #8 |
|---|---|---|---|---|---|---|
| lb/ft | 0.376 | 0.668 | 1.043 | 1.502 | 2.044 | 2.670 |
This is the easy 20%. The other 80% is on your drawings.
A grid calculator prices the flat mats you already understand. What it can’t do is read your structural set: it can’t read your bar schedules, bend types and section details, the corner bars and standees, the dowels lapping into the next pour, the extra top steel over a beam, or the trim around an opening. That’s the part of a concrete bid that leaks money — and it’s exactly what Pilars AI takeoff does from your actual plans: it reads the schedules, classifies every bar mark and bend, and returns the full rebar takeoff by size. $100 per trade, per plan.
Questions estimators actually ask
How does the calculator count bars?
For each element it lays out a two-way grid. Bars running lengthwise = width × 12 ÷ spacing, rounded up, plus one closing bar; each runs the full length. Bars running widthwise = length × 12 ÷ spacing, rounded up, plus one; each runs the full width. Multiply by the number of mats for total linear feet.
How does it convert rebar to weight and tons?
Each bar size has a unit weight in pounds per foot — #3 0.376, #4 0.668, #5 1.043, #6 1.502, #7 2.044, #8 2.670. Total linear feet (including lap and waste) × the unit weight gives pounds, and pounds ÷ 2,000 gives tons.
Does it include lap splices and waste?
Yes — a single lap-and-waste percentage (default 15%) is added to the bare grid length. That covers typical 40-bar-diameter lap splices and ordinary cut waste. Change it to match your bar lengths and splice schedule.
Does it calculate tie wire and bar chairs?
Yes. Tie wire is estimated at about 16 lb per ton of rebar, ordered in 3.5-lb rolls. Bar chairs and supports are estimated at one per 9 SF of mat area, per mat. Dowels, corner bars and standees are not in a length-based calc — they come from the structural details.
Is this as accurate as a real plan takeoff?
It’s a fast estimating tool built on standard industry factors and a simple rectangular grid. It doesn’t read your bar schedules, bend types, section details, dowels or standees — that’s what Pilars does from your actual drawings for $100 per trade.
Let Pilars take off your whole set.
Upload your plans. Pilars reads the bar schedules, applies bend types and section details, catches dowels, corner bars and standees, and returns the full rebar takeoff by size and weight. $100 per trade.