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Cut lengths, weight and 12 m bars for each size
The cut length is the bar length.
1 of 60 rows
A mesh of straight bars in both directions.
The least cover of a slab in mild conditions is 2 cm.
The structural drawing sets the bar size and spacing; this works out the count and length from the geometry.
The length of the bars you buy; the default is 12 m and the cutting plan is laid out on this length.
Site rule: a 90° hook, 15 × diameter.
Site rule: stirrup perimeter + 20 cm.
For a bar longer than one branch; site rule 40 × diameter.
3 per cent on a large project, 5 per cent on a small one.
Weight to buy
—kg
The result appears hereEnter the diameter, shape, dimensions and count of each bar.
Basis: Weight per metre = diameter² ÷ 162. The number of bars comes from laying the cut pieces out on 12 m bars.
Keep the final list, and its cost at each day’s prices, here:Project shopping list
Method
Bar weight: the diameter in millimetres squared, divided by 162, is the weight of one metre in kilograms; the same figure the Ahantime weight calculator shows.
End hook: each 90° hook adds 15 × the bar diameter to the length without hooks. “Hook at one end” has one, “hook at both ends” two.
Closed stirrup: the cut length is the stirrup perimeter (twice the sum of the two sides) plus 20 cm for the two hooks. The sides are the stirrup’s own, not the concrete section’s.
Lap: a bar longer than a 12 m branch is made of pieces that overlap by 40 × the diameter; that length is added to the steel used.
Number of bars: the pieces, longest first, are laid out on 12 m bars to find how many are needed to cut them; three 7 m bars need three branches, not two. With 5 per cent waste, the count is never below the total length plus waste. The left-over is the length bought minus the net length of the list.
Every rule is a site default and can be changed under “Calculation rules”. The size, number, hook length and lap length of each bar are set by the structural drawings and the design engineer.
Reference table
Weight per metre and per 12 m bar, with the default hook and lap length of each size.
| Diameter (mm) | Weight per metre (kg) | Weight of a 12 m bar (kg) | Hook length (cm) | Lap length (cm) |
|---|---|---|---|---|
| 8 | 0.395 | 4.74 | 12 | 32 |
| 10 | 0.617 | 7.41 | 15 | 40 |
| 12 | 0.889 | 10.67 | 18 | 48 |
| 14 | 1.21 | 14.52 | 21 | 56 |
| 16 | 1.58 | 18.96 | 24 | 64 |
| 18 | 2 | 24 | 27 | 72 |
| 20 | 2.469 | 29.63 | 30 | 80 |
| 22 | 2.988 | 35.85 | 33 | 88 |
| 25 | 3.858 | 46.3 | 37.5 | 100 |
| 28 | 4.84 | 58.07 | 42 | 112 |
| 32 | 6.321 | 75.85 | 48 | 128 |
The perimeter is 140 cm; with 20 cm for the hooks the cut length is 1.6 m. One stirrup weighs 0.632 kg and a 12 m bar gives 7 of them.
The site rule is 15 × the diameter for each 90° hook; 24 cm for a 16 mm bar. A 5 m bar hooked at both ends is cut at 5.48 m.
The site rule is 40 × the diameter; 80 cm for a 20 mm bar. A 15 m bar of size 20 is made of 2 pieces and takes 15.8 m of steel. The design engineer gives the exact lap on the drawing.
Because each piece must be cut from one bar. Three 7 m bars are 21 m in all, yet need 3 bars and leave 15 m over. The tool works out the cutting layout.
The tool’s default is 5 per cent: 3 per cent on a large project and 5 per cent on a small one. Change it under “Calculation rules”.
Choose a mill for each size to see the amount at today’s price; then tap “Add to cart”, “Add to project shopping list” or “Proforma”. There is no online payment; an Ahantime expert calls to close the purchase.