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Rebar calculator

Rebar shopping is length and weight. Spacing on a slab grid gives you how many sticks; bar size (#3 / #4 / #5) turns length into pounds so the yard can quote. This page does not design reinforcement for loads. If a footing carries a house, the schedule comes from drawings — not a browser grid.

ft
ft
in
ft
10%
0510152025

+10% so you don't come up short

ORDER ESTIMATEREBAR
Total length154 ft
Approx. weight103 lb
Sticks to buy8
Lap adder10%
How it calculates
bars each way = floor(span ÷ spacing) + 1; total length = Σ(count × bar length) × (1 + lap%); weight = length × lb/ft; sticks = ceil(length ÷ stick).

Materials estimate only — not structural design. Follow drawings for load-bearing work.

When to use

Shed slab grid shopping; comparing #3 vs #4 weight for a budget; estimating how many 20 ft sticks to buy.

When not to

Engineered foundations, post-tension slabs, epoxy-coated schedules with lap splice details from a PE — follow the drawings.

Assumptions

Rectangular grid: bars each way at spacing. Lap splices optional adder %. Weight per foot uses common published unit weights (#3 ≈ 0.376 lb/ft, #4 ≈ 0.668, #5 ≈ 1.043). Waste/laps default editable.

Worked examples

Example 1

10×10 slab, #3 @ 18 in each way, 20 ft sticks
→ 8 bars each way × 10 ft = 160 ft → weight ≈ 60 lb → buy sticks of 20 ft with cuts/laps as you detail

Chairs and tie wire are separate.

Example 2

20×4 footing strip, #4 continuous with lap 10%
→ length × 1.1 → weight from #4 lb/ft

How it calculates

Count bars each way from spacing, sum lengths with lap %, convert to weight and sticks.

  1. Enter slab or footing rectangle and bar spacing.
  2. Pick #3 / #4 / #5 and stick length.
  3. Set lap percent; read total feet, pounds, and sticks.
bars each direction ≈ floor(length ÷ spacing) + 1
total length = Σ (count × bar_length) × (1 + lap%)
weight ≈ total length × lb/ft
sticks = ceil(total length ÷ stick_length)

Common traps

  1. Clear cover changes how bars fit — not in the weight formula.
  2. Lap length is code/bar-size dependent; our % adder is a shopping cushion.
  3. Mesh vs rebar — WWM is a different product; do not mix counts.
  4. Metric bar sizes use different unit weights.

Next tool

Concrete volume for the same pour → concrete calculator / slab.

Block walls with horizontal bond beam steel — still a schedule problem first.

FAQ

Count bars each way from spacing, sum lengths, convert to weight.

Related

Estimate only — not a contractor bid or engineered takeoff. Confirm bag yields and local codes before you pour or order.