Rebar Tonnage Calculator

Why two ton units

The word ton covers two different units of mass. A US short ton is 2,000 lb and is the ton a US rebar yard quotes in. A metric tonne (t) is 1,000 kg = 2,204.62 lb and is the ton a metric supplier, a non-US engineer, or an export invoice quotes in. The two are 10.2% apart: the metric tonne is the heavier of the two by exactly 204.62 lb.

The 10.2% gap is not rounding error. On the 18 ft × 16 ft slab the takeoff is 591.9 lb. At a $700/ton price the quote is $207.17 in short tons and $187.93 in tonnes — a $19 swing on one slab, on one material, for the same piece of steel. A rebar tonnage calculator has to pick the right ton for the supplier it is feeding, or report both and let the user pick.

The split between the takeoff and the order is the other thing this page works through. The takeoff is the net steel in the structure (567.5 ft, 591.9 lb on the worked example). The order is the whole bars you actually buy (34 bars of 20 ft, 680 ft, 709.2 lb). The order is the number to hand the supplier, and it is always larger than the takeoff by the off-cut percentage. Everything below runs on the 18 ft × 16 ft slab in #5 bar at 12 in o.c. with 1.5 in cover.

Step 1 — total bar length to pounds

First turn the bar layout into a total length, then a total weight. The layout on a slab grid is the same job the slab rebar page walks through: floor( clear / spacing ) + 1 bars in each direction, each bar as long as the slab dimension it runs. On the 18 ft × 16 ft slab the two counts come off the two different dimensions:

The 1.043 lb/ft is the nominal unit weight of a #5 bar — the conversion factor that turns a length in feet into a weight in pounds. Each bar size has its own number, and the table is short enough to keep on hand:

Swipe the table sideways for more columns →

lb/ft and kg/m are the nominal ASTM A615 / A706 unit weights; the total length comes from the layout in Step 1.

Multiply feet by the lb/ft for the bar size on the drawing and you have the takeoff in pounds. The conversion to tons is the next step. The weight page runs the same multiplication for a single bar, a stock length, or a whole order.

Step 2 — pounds to short tons or tonnes

Two divisions, one for each ton. Same takeoff (591.9 lb), two answers, and the two answers are not the same number:

The gap is mechanical: a metric tonne is 1.10231 short tons. Multiply the tonnes by 1.10231 to get short tons; multiply the short tons by 0.90718 to get tonnes. The two units are right answers to two different questions, and a tonnage calculator that only reports one of them is half a tool.

Swipe the table sideways for more columns →

Pounds to short tons is ÷ 2,000 and to metric tonnes ÷ 2,204.62; the cost line uses the $700 per short ton in the header.

The cost column shows why the unit choice matters. At $700/ton the takeoff costs $207.17 in short tons and $187.93 in tonnes — the same piece of steel, $19 apart, because the tonne is the heavier unit. Always confirm which ton the supplier has on the quote before comparing two prices. The takeoff itself is the same in both columns; the division is the only thing that changes.

Bar weights are nominal ASTM A615 / A706 values. Coated or stainless bar changes the lb/ft — use the project value when the drawing calls it out. The size and weight chart has the full table from #3 to #18.

Watch: weight to tons and bars per ton

Step 3 — tons to bars, and the order tonnage

The reverse question is the one a buyer actually asks: we need 2 tons of #4 on 20 ft stock — how many bars is that? The conversion is the same lb/ft table, just arranged differently. One short ton is 2,000 lb; one short ton of #4 on 20 ft stock is 2,000 ÷ (0.668 × 20) = 149.7 bars, rounded down to 149 whole bars you can buy. One metric tonne is 2,204.6 lb; the same #4 on 20 ft stock is 2,204.6 ÷ (0.668 × 20) = 165.0 bars, 165 whole bars. 40 ft stock halves both counts, because each bar now carries twice the steel.

Swipe the table sideways for more columns →

Bars per ton is 2,000 ÷ (lb/ft × stock length), rounded down; the order tonnage adds the waste allowance stated above.

The bars-per-ton column is what a buyer uses to translate a tonnage into a purchase order, but the number the rebar yard actually delivers is the order tonnage, not the takeoff tonnage. Going back to the 18 ft × 16 ft slab, the order is 34 bars of 20 ft = 680 ft = 709.2 lb. In short tons that is 0.355; in tonnes it is 0.322. The takeoff was 0.296 / 0.269. The order is 20% heavier than the takeoff, and that 20% is the off-cut on 34 bars — the 4.25 ft scrap from each 15.75 ft piece and the 2.25 ft scrap from each 17.75 ft piece, summed.

The order tonnage is the tonnage to buy. The takeoff tonnage is the tonnage in the structure; the order tonnage is what leaves the yard. On the worked slab the order is 0.355 short tons against a takeoff of 0.296, a gap of 0.059 short tons that is the price of buying steel in fixed lengths. The estimator page runs the same off-cut analysis in pieces and feet, and the weight page takes a single bar, a stock length, or a whole order straight to pounds.

Pounds of rebar per cubic yard of concrete

The question how much rebar per cubic yard of concrete is a budgeting question, not a design one. The engineer picks the bar size, the spacing, and the slab thickness; the cubic-yard ratio is what falls out. It is useful for two things: checking whether a pour is in the normal range before the steel arrives, and converting a concrete volume on a bid sheet into a rough rebar tonnage without a full takeoff.

The formula

The 27 is the cubic-feet-to-cubic-yard factor (3 × 3 × 3 = 27). The lb_per_ft is the nominal ASTM A615 unit weight: 0.668 for #4, 1.043 for #5, 1.502 for #6. Everything else comes off the drawing.

Worked on the page example: 18 ft × 16 ft, #5 @ 12 in, 6 in slab

The takeoff from Step 1 is 567.5 ft of #5 = 591.9 lb. The concrete volume is 18 × 16 × 0.5 ft = 144 cf = 5.33 cy. Pounds per cubic yard:

Same slab in #4 @ 12 in: the bar layout is identical (567.5 ft), but #4 is 0.668 lb/ft instead of 1.043, so the takeoff drops to 379.1 lb and the ratio drops to 71.1 lb/cy. The bar size is the lever; the spacing and the slab thickness move it too, but the bar size moves it the most.

Five structures side by side

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All five are worked from the layout formulas on this site: slabs from the slab page, wall from the wall page, footing from the footing page. Bar weights are nominal ASTM A615 values.

Why the range is so wide

The ratio moves for three reasons, and only one of them is the bar size:

• Bar size — switching #4 to #5 on the same layout nearly doubles lb/ft (0.668 → 1.043), and the ratio follows. The #5 slab at 111 lb/cy vs the #4 slab at 72 lb/cy is the same 567.5 ft of bar carrying 213 more pounds.
• Spacing — tightening from 16 in to 12 in adds a third more bars. On the 4 in slab that moves the ratio from 80 to roughly 107, because the thinner slab has less concrete to spread the weight over.
• Thickness — a thicker slab adds concrete volume without adding bar, diluting the ratio. The same #4 @ 12 in layout at 6 in thick is 72 lb/cy; at 4 in thick it would be 108 — same steel, more concrete, lower ratio.

Because all three move at once, a single lb/cy number quoted without a bar size, a spacing, and a thickness is a guess. The table above is the range you will see in residential and light commercial work; heavy commercial with #6 and #8 at tight spacing can run 150–200 lb/cy, and a mat footing with top and bottom mats can exceed 250.

Reverse: from a concrete volume to a rebar tonnage

If a bid sheet gives a concrete volume and no rebar takeoff, the ratio works in reverse. A 50 cy pour at 72 lb/cy is roughly 3,600 lb of rebar = 1.8 short tons. The number is a planning figure, not an order — it carries no off-cut, no lap allowance, and no waste factor. For the actual order, run the estimator on the real layout and add the off-cut.

Planning figures, not quotes — the ratio is a midpoint, not a specification. The actual takeoff depends on the layout, the lap detail, and the stock length, all of which come from the drawing.

Common questions

How many pounds of rebar are in a ton?

It depends on which ton. A US short ton is 2,000 lb, and a metric tonne (t) is 2,204.62 lb — 10.2% heavier. A "ton" of rebar is 2,000 lb in the US system and 2,204.62 lb in the metric system. A rebar tonnage calculator converts a takeoff or order weight in pounds to tons in the right unit: divide by 2,000 for short tons, or by 2,204.6 for tonnes.

How do you calculate rebar tonnage?

Two steps, then a division. First multiply the total bar length in feet by the lb/ft for the bar size to get the takeoff weight in pounds. Then divide by 2,000 for US short tons or by 2,204.6 for metric tonnes. For the order, multiply the number of bars by the stock length and by lb/ft, then divide by the same ton factor. On the 18 ft × 16 ft slab the takeoff is 591.9 lb = 0.296 short tons = 0.269 tonnes; the order on 20 ft stock is 709.2 lb = 0.355 short tons = 0.322 tonnes.

How many #4 rebar are in a ton?

149 bars of #4 in 20-ft stock per US short ton (149.7 exact, rounded down to whole bars you can buy). Per metric tonne it is 165 bars (165.0 exact). The exact count is ton_lb ÷ (lb_per_ft × stock_length): 2,000 ÷ (0.668 × 20) for short tons, 2,204.6 ÷ (0.668 × 20) for tonnes. On 40-ft stock the same ton holds half as many bars: 74 per short ton, 82 per tonne.

How many tons of rebar do I need for a slab?

Compute the takeoff first, then the order, and order by the order tonnage. For an 18 ft × 16 ft slab in #5 bar at 12 in o.c. both ways with 1.5 in cover: takeoff 567.5 ft = 591.9 lb = 0.296 short tons = 0.269 tonnes; order 34 bars of 20 ft = 680 ft = 709.2 lb = 0.355 short tons = 0.322 tonnes. The order is the number to buy, because the takeoff ignores the off-cut on every bar.

Is a metric tonne and a US short ton the same?

No. A metric tonne (t) is 1,000 kg = 2,204.62 lb. A US short ton is 2,000 lb. A metric tonne is 10.2% heavier than a US short ton, so quoting a rebar price in dollars per tonne versus dollars per short ton changes the effective cost by 10.2%. On the worked example a $700/ton price comes out to $207.17 in short tons and $187.93 in tonnes — the same piece of steel, $19 apart, for picking the wrong ton.

Should I order by takeoff weight or order weight?

Order by the order weight, which is bars × stock × lb_per_ft. The takeoff is the net length of steel in the structure and is always less than the order by the off-cut percentage. On the 18 ft × 16 ft slab the takeoff is 591.9 lb and the order is 709.2 lb — a 20% gap. If you order by the takeoff you will run short by exactly that off-cut on the last bar.

How do I convert rebar length to tons?

Two multiplications and a division. total_lb = total_feet × lb_per_ft (0.376 for #3, 0.668 for #4, 1.043 for #5, 1.502 for #6, 2.670 for #8). Then tons_short = total_lb ÷ 2,000; tons_metric = total_lb ÷ 2,204.6. The two values differ by 10.2% — pick the unit your supplier quotes in. The reverse direction (a tonnage target to a bar count) is bars = floor( ton_lb ÷ (lb_per_ft × stock_length) ).

How many pounds of rebar per cubic yard of concrete?

A typical slab on grade runs 70 to 110 lb of rebar per cubic yard of concrete. A wall runs about 40, a strip footing about 55. The number is takeoff_lb ÷ concrete_cy, where concrete_cy is length_ft × width_ft × thickness_ft ÷ 27. On the worked 18 ft × 16 ft slab in #5 at 12 in on centre, the takeoff is 591.9 lb and the volume is 5.33 cy, giving 111 lb/cy. The same slab in #4 at 12 in gives 72 lb/cy. The bar size is the biggest lever: switching #4 to #5 on the same layout raises the ratio by about half.

What this page does not do

Related

• Rebar calculator — bar counts, laps, lengths, weight and cost for a slab grid
• Rebar weight calculator — pounds per foot, per bar and per order
• Rebar estimator — off-cut, not percentage, with a worked lap trade
• Calculate rebar for a slab — the grid formulas and the lap allowance
• Rebar spacing calculator — spacing into rows and columns and a cut list
• Rebar grid calculator — two spacings on one slab, with the shared-bar correction
• Rebar calculator for wall — verticals along the length, horizontals up the height
• Footing rebar calculator — the 20 ft vs 40 ft trade for a strip footing
• Rebar size & weight chart — #3 to #18 and 10 mm to 40 mm, with unit weights
• Rebar splicing — lap, mechanical and welded compared with costs

Published 9 October 2026 · Last reviewed 3 November 2026