Rebar Weight Calculator
Estimate the weight of steel reinforcement bar (rebar) from its size and total length for material ordering and crane-load planning. Useful for concrete contractors, structural engineers, and quantity surveyors.
Last updated: May 2026
Compare with similar
About this calculator
Steel rebar is sold and shipped by weight; total weight scales linearly with both length and the bar's mass per unit length. The standard relationship is Weight (lb) = (mass per foot in lb/ft) × Length (ft), where mass per foot depends on the bar's nominal diameter. The implementation here reads the bar's published mass per foot directly from the size you select (e.g. #4 = 0.668 lb/ft) and multiplies by total length: Weight (lb) = (lb/ft) × Length (ft). The cleaner reference is the published lb/ft table: #3 (9.5 mm dia, 3/8″) = 0.376 lb/ft; #4 (12.7 mm, 1/2″) = 0.668 lb/ft; #5 (15.9 mm, 5/8″) = 1.043 lb/ft; #6 (19.1 mm, 3/4″) = 1.502 lb/ft; #7 (22.2 mm, 7/8″) = 2.044 lb/ft; #8 (25.4 mm, 1″) = 2.670 lb/ft; #9 (28.7 mm, 1-1/8″) = 3.400 lb/ft; #10 (32.3 mm, 1-1/4″) = 4.303 lb/ft; #11 (35.8 mm, 1-3/8″) = 5.313 lb/ft. Variables: bar size designation (US Imperial #3–#18 corresponds to 1/8-inch increments of diameter), total length in feet (sum across all pieces). Edge cases: epoxy-coated bar is ~3% heavier than plain due to coating thickness, but most weight calculators ignore this. Stainless steel rebar (ASTM A955) is the same nominal diameter but slightly less dense; weight is ~98% of carbon steel. Galvanized rebar is similar to plain (zinc coating <1% of weight). Always order 5–10% over net to allow for cutting waste and overage tolerance on bundled deliveries.
How to use
Example 1 — slab reinforcement. A 20 ft × 30 ft slab uses a #4 (1/2″) rebar grid on 12″ centers in both directions. Step 1: count of bars in the long direction = (30 / 1) + 1 = 31 bars, each 20 ft long → 31 × 20 = 620 ft. Step 2: count in the short direction = (20 / 1) + 1 = 21 bars, each 30 ft long → 21 × 30 = 630 ft. Step 3: total length = 620 + 630 = 1,250 ft. Step 4: #4 weighs 0.668 lb/ft → total weight = 1,250 × 0.668 = 835 lb. Verify: at 167 ft per 20 ft bar (8.35 standard 20-ft sticks), call it 63 bars of 20 ft = 1,260 ft, weight 842 lb. Close enough — order 1,300 ft (about 65 × 20-ft bars) to allow 4% extra. Example 2 — footing rebar order. A continuous footing requires 480 ft of #6 (3/4″) rebar plus 320 ft of #4 (1/2″) stirrups. Step 1: #6 weight = 480 × 1.502 = 720.96 lb. Step 2: #4 weight = 320 × 0.668 = 213.76 lb. Step 3: total = 720.96 + 213.76 = 934.72 lb ≈ 935 lb. Verify: bars come bundled in standardized loads; one ton (2,000 lb) of #6 holds about 1,331 ft, so 480 ft = 36% of a ton bundle. Suppliers typically deliver in 1-ton or 5-ton bundles; round your order up to bundle quantities for best pricing.
Frequently asked questions
What are the standard rebar sizes and their weights per foot?
US imperial rebar sizes use a number that equals the nominal diameter in eighths of an inch: #3 = 3/8″ = 9.5 mm = 0.376 lb/ft; #4 = 1/2″ = 12.7 mm = 0.668 lb/ft; #5 = 5/8″ = 15.9 mm = 1.043 lb/ft; #6 = 3/4″ = 19.1 mm = 1.502 lb/ft; #7 = 7/8″ = 22.2 mm = 2.044 lb/ft; #8 = 1″ = 25.4 mm = 2.670 lb/ft. Larger sizes used in heavy commercial and bridge work: #9 = 3.400 lb/ft, #10 = 4.303 lb/ft, #11 = 5.313 lb/ft, #14 = 7.65 lb/ft, #18 = 13.60 lb/ft. Metric rebar designations (M10, M13, M16, etc.) refer to nominal diameter in millimeters. ASTM A615 covers Grade 40, 60, and 75 carbon-steel rebar; A706 covers low-alloy weldable rebar with controlled ductility for seismic zones. Higher grades have the same weight per foot — only yield strength differs.
Does rebar weight differ between epoxy-coated, galvanized, stainless, and plain carbon steel bars?
Plain carbon steel rebar (ASTM A615) is the baseline and the weights in standard tables. Epoxy-coated rebar (ASTM A775/A934) adds 0.005–0.015 inches of coating thickness per face; total weight is about 3% higher than plain for #4 and smaller sizes, decreasing to about 1% for #11 and larger. Galvanized rebar (ASTM A767) has a thin zinc coating (1–2 mils typical) adding less than 1% to weight — usually treated as the same as plain for ordering. Stainless steel rebar (ASTM A955) has the same nominal diameter but slightly lower density (about 7.85 g/cm³ for type 316, versus 7.85 for plain carbon — essentially equal); weight is within ±1% of plain. Glass-fiber-reinforced-polymer (GFRP) rebar is about 25% the weight of steel for the same nominal size, used in corrosive environments. For weight estimates use plain-steel tables as a baseline and adjust upward by 3% only if specifying epoxy-coated for visible structural calculation purposes.
How much rebar overage should I order for a typical job to account for cuts and waste?
Standard waste allowance for rebar is 5–10% over net required length. Slab and footing work with long straight runs: 5% (minimal cutting). Walls and beams with stirrups, ties, and bent shapes: 10% (more cutting waste). Heavy seismic detailing with closely-spaced ties and hooks: 12–15% (high cut intensity). Bundling and shop fabrication also affects delivery: rebar is typically delivered in 20-ft, 30-ft, 40-ft, or 60-ft lengths, and bundles are often standardized to 2-ton or 5-ton loads. Ordering precise quantities below a full bundle often incurs a small bundle-break fee. For shop-fabricated and pre-bent rebar (orders detailed via a bar list), you pay for the fabricated length plus typical 2–5% overage. Lap splices add additional length: for tension splices the lap is typically 40–60× bar diameter, which for a #5 with 50d lap adds 31″ per splice — count these in your length calculation.
What are common mistakes when calculating rebar weight and quantity?
The most frequent mistake is forgetting lap splices. A 60-ft continuous bar called for on plans is typically delivered in 20-ft or 40-ft sticks requiring laps, adding 5–10% length depending on splice type and frequency. Confusing bar size (#4) with bar diameter (1/2″) or with weight per foot leads to factor-of-2+ errors when transferring numbers between drawings and suppliers. Using metric vs. imperial designations inconsistently — calling a #5 bar 16 mm (close but not quite — actual is 15.9 mm) — can mismatch what is on plans vs. ordered, especially in international projects. Forgetting stirrup, tie, and hook bends — a typical column tie has six 90° bends adding 6 × 8d = 48d of straight equivalent per tie. Ignoring development length (anchorage) at column-to-footing or beam-to-column joints under-estimates required length. Finally, computing weight from the formula but using a bar size designator (e.g., '5') as a diameter (in mm or inches) in the formula gives wildly wrong answers — verify the calculator's input convention before keying in numbers.
When should I NOT use this calculator?
Skip simple bar-size × length weight calculations for final structural takeoffs on commercial or public works projects — those require a detailed bar list and shop drawings reviewed by an SE/PE, with bar marks, bend schedules, and shop-fabricated quantities, not just a total weight. Do not use it for international projects where ISO, BS, or DIN rebar standards apply — diameters, grades, and yield strengths are differently designated and the weight tables differ. Avoid it for prestressing steel (PT strands, deformed bars in PT systems) which uses different ASTM standards (A416, A722) and different weight conventions. The formula is also inappropriate for fiber-reinforced concrete or steel-fiber composite reinforcement, which is sold by weight in entirely different units (lb per cubic yard of concrete). For seismic detailing where strict ductility and confinement matter (ACI 318 Chapter 18), the bar quantities are driven by detailing rules that go far beyond simple weight estimates — consult the structural drawings and ACI commentary. Finally, never use a weight calculator as a substitute for the structural engineer's bar schedule — quantities on plans are authoritative, and substituting your own estimate creates liability.