Answer: Enter your values and the Rebar Calculator returns the exact result instantly — formula, worked example, and a plain-English explanation are included below the tool.
Rebar grid, sticks, tie wire & cost for slabs and footings
This rebar calculator estimates the total length, weight, and stick count of reinforcing bar for slabs, footings, and walls. Enter dimensions, bar size, and spacing, and the tool works out linear footage, weight in pounds, and how many 20-foot sticks to order.
Rebar estimating is built on two published facts: each bar size has an ASTM unit weight, and grid spacing determines how many bars cross a given length.
Bar count in each direction = floor(length in inches ÷ spacing in inches) + 1, because a bar occupies both ends. Total linear feet = (bars one way × length) + (bars the other way × width). Weight uses ASTM A615 unit weights: #3 is 0.376 lb/ft, #4 is 0.668 lb/ft, #5 is 1.043 lb/ft, #6 is 1.502 lb/ft, #7 is 2.044 lb/ft, and #8 is 2.670 lb/ft.
Sticks to buy = total linear feet ÷ 20 (the standard stock length), rounded up, plus a few extra for laps. Lap splices are typically 30 to 40 times the bar diameter, so a #4 bar (4/8 inch) needs roughly 12 to 20 inches of overlap wherever bars join.
The table lists each bar size's unit weight and the computed totals for 1,000 linear feet of bar — a convenient planning quantity. One US ton is 2,000 pounds, so the ton column shows how many 20-foot sticks make a ton.
For example, 1,000 feet of #4 bar weighs 668 pounds (1,000 × 0.668), and a ton of #4 is about 150 sticks.
| Bar size | Weight (lb/ft, ASTM A615) | 1,000 lf weight | 20-ft sticks per ton (2,000 lb) |
|---|---|---|---|
| #3 (3/8 in) | 0.376 | 376 lb | 266 |
| #4 (1/2 in) | 0.668 | 668 lb | 150 |
| #5 (5/8 in) | 1.043 | 1,043 lb | 96 |
| #6 (3/4 in) | 1.502 | 1,502 lb | 67 |
| #7 (7/8 in) | 2.044 | 2,044 lb | 49 |
| #8 (1 in) | 2.670 | 2,670 lb | 38 |
For a 10×10 slab with #4 bar at 18 inches on center each way: each direction is 120 inches, so floor(120 ÷ 18) + 1 = 7 bars. Total length is 7 × 10 + 7 × 10 = 140 linear feet, which weighs 140 × 0.668 = 93.5 pounds — exactly 7 twenty-foot sticks.
Common slab practice per CRSI and ACI 318 guidance places reinforcement at the slab's lower third with chairs supporting it, uses #3 or #4 bar at 12 to 18 inches on center for light residential slabs, and requires concrete cover of at least 2 inches where slab contacts ground. Always follow your engineer's or code's specified spacing.
Ordering by weight keeps quotes comparable across suppliers. Because a #4 stick weighs 13.4 pounds, a small residential job of 140 linear feet is only 93.5 pounds — often too small for mill-direct delivery, so box-store bundles (usually ten sticks) are the practical unit. For larger jobs, fabricators can cut and bend bars to your schedule, which reduces on-site waste and labor.
Support the grid on chairs or bricks so the steel sits in the slab's lower third — rebar lying on the ground does almost nothing structurally. Use one chair roughly every 24 to 30 inches in both directions. Tie intersections with 16-gauge tie wire, twisting with a wire twister; figure about 3 pounds of wire per 1,000 square feet of mesh.
Safety and handling matter on any pour: gloves prevent cuts and wire pokes, and heavy #6 and larger bars deserve two-person carries. Never walk an unsupported grid mid-pour, and make sure your placement matches the inspected drawings — field changes to spacing or bar size should always go back through the engineer of record.
How much does rebar weigh per foot?
ASTM A615 unit weights per foot are: #3 is 0.376 lb, #4 is 0.668 lb, #5 is 1.043 lb, #6 is 1.502 lb, #7 is 2.044 lb, and #8 is 2.670 lb. Multiply total linear feet by the unit weight to get pounds.
How many sticks of rebar do I need for a 10x10 slab?
A 10×10 slab with #4 bar at 18 inches on center each way needs 7 bars per direction = 140 linear feet, which is exactly 7 twenty-foot sticks (93.5 lb). Order a couple extra for laps and tie wire.
How is rebar spacing measured?
Spacing is the on-center distance between parallel bars. For each direction, bar count = floor(length in inches ÷ spacing) + 1. Common residential spacings are 12 and 18 inches on center; local code or engineering drawings govern the required value.
How long should rebar lap splices be?
Tension lap splices are typically 30 to 40 times the bar diameter depending on concrete strength and conditions — roughly 12 to 20 inches for #4 bar. ACI 318 tables give exact values; when in doubt, overlap by at least 24 inches for small bars.
How do I convert rebar weight to tons?
Divide total pounds by 2,000 to get US tons. For example, 1,000 linear feet of #4 bar weighs 668 pounds, or 0.334 tons. Suppliers often price by the ton, so weight-based quotes make comparing easy.