Cutting Length Calculator for Rebar Shapes
Cutting length is the straight bar length you need to cut before bending a reinforcement shape. This calculator focuses on one bar at a time: pick a stirrup, circular ring, cranked bar or straight bar with hooks, enter the dimensions from the drawing, and it shows the cut length with every segment, hook allowance and bend deduction exposed.
The model is deliberately smaller than a bar bending schedule. It does not manage marks, quantities, shape codes or a project schedule. It is for checking one shape quickly, explaining the formula, and printing a clear calculation that can be reviewed on site.
All calculations run in millimetres in your browser. The default hook allowance follows the IS 2502 mild-steel form, 9d with a 75 mm minimum and 5 mm rounding. The bend deduction ladder is an adjustable field approximation: 45 degrees is 1d, 90 degrees is 2d, 135 degrees is 3d and 180 degrees is 4d.
How to calculate rebar cutting length
The calculator uses the same general structure for every shape: add the centre-line straight or curved segments, add hook allowances where hooks exist, then subtract bend deductions where the shape has sharp bends.
For stirrups, the outer drawing dimensions are reduced by cover to get the centre-line dimensions. For rings, the centre-line diameter is the outer diameter minus twice the cover and one bar diameter. For cranked bars, the crank extra is geometric: the vertical offset multiplied by cosecant θ minus cotangent θ.
Cutting length in 5 steps
- Choose the bar shapeSelect rectangular stirrup, square stirrup, circular ring, cranked bar or straight bar with hooks.
- Enter drawing dimensionsFill in the dimensions shown on the labelled diagram, including bar diameter and cover where the shape uses them.
- Check hooks and bendsUse the default 9d hook allowance and bend ladder, or open the advanced model to match your site convention.
- Read the breakdownReview the total cut length, metres value, formula substitution, segment additions, hook additions and bend deductions.
- Print the calculationPrint the single-shape sheet when you need a compact record for checking, cutting or discussion.
Cutting length formulas by shape
Use the formula that matches the bar shape you are checking. The live result panel above substitutes your entered dimensions into the same expression and lists the signed terms.
These are the formulas used by the calculator. H is the hook allowance, BD is bend deduction, d is bar diameter and c is cover.
Rectangular stirrup
L = 2(a + b) + 2H - 3BD90, where a = A - 2c and b = B - 2c- A and B are the outside width and height.
- The default model adds two hooks and deducts three 90 degree bends.
- Cover is applied to the centre-line dimensions before the perimeter is calculated.
Square stirrup
L = 4a + 2H - 3BD90, where a = S - 2c- S is the outside square side.
- The square shape uses the same hook and bend model as the rectangular stirrup.
- Use it when both stirrup sides are equal and you want a simpler input set.
Circular ring
L = pi x D_c + nH, where D_c = D_out - 2c - d- D_out is the outside diameter of the circular tie.
- The default ring uses centre-line circumference plus the selected number of hooks.
- Sharp bend deductions default to zero for this smooth centre-line ring model.
Cranked bar
L = L_m + n x D_v x (csc θ - cot θ) - 2nBDθ- L_m is the member length measured as if straight.
- At 45 degrees, the crank extra is about 0.42 x D_v per crank.
- The default model deducts two bends for each crank.
Straight bar with hooks
L = L0 + nH- L0 is the base straight length before end hooks.
- n is the number of hooked ends, from zero to two.
- Hook bend effects are included in the hook allowance, so separate bend deductions default to zero.
Hook allowance and bend deduction reference
The tables below show the default model behind the calculator. Hook allowance factors are derived from the pinned IS 2502 family in the engine constants. Bend deductions use the local angle ladder that the calculator exposes in the advanced model.
| IS 2502 family | Hook factor | Minimum | Rounding |
|---|---|---|---|
| Mild steel | 9d | 75 mm | 5 mm |
| Medium tensile | 11d | 75 mm | 5 mm |
| Cold-worked | 13d | 75 mm | 5 mm |
| Cold-worked over 25 mm | 17d | 75 mm | 5 mm |
| Bend angle | Deduction |
|---|---|
| 45° | 1d |
| 90° | 2d |
| 135° | 3d |
| 180° | 4d |
Hook factors, minimum and rounding are pinned from the IS 2502:1963 family used by the engine. The 1d/2d/3d/4d bend ladder is an angle-based field approximation and can be edited in the advanced model.
Frequently asked questions
What is rebar cutting length?
Cutting length is the straight length of reinforcement bar to cut before it is bent into the final shape. It starts from the centre-line segments of the shape, then adds hook allowances and subtracts bend deductions where they apply.
How do I calculate the cutting length of a stirrup?
For a rectangular stirrup, use L = 2(a + b) + 2H - 3BD90, where a and b are the centre-line width and height after cover. This calculator derives a and b from the outside dimensions and cover, then applies the selected hook and bend model.
What is bend deduction?
Bend deduction removes the extra length counted when straight outside dimensions are turned into a bent centre-line shape. The default ladder here is 45 degrees = 1d, 90 degrees = 2d, 135 degrees = 3d and 180 degrees = 4d. It is a field approximation, so the values are editable.
What hook length does the calculator use?
The default hook allowance is max(9d rounded to the nearest 5 mm, 75 mm), matching the IS 2502 mild-steel factor family pinned in the calculator engine. You can change the factor in the advanced model.
How is crank length of a bar calculated?
For each crank, the added length is D_v x (csc θ - cot θ). At 45 degrees this is 0.4142 x D_v, commonly rounded to 0.42D. The calculator then subtracts the selected bend deduction for the two kinks in each crank.
How is circular ring cutting length calculated?
The default ring formula is pi x D_c + nH, where D_c is the centre-line diameter: outside diameter minus twice the cover minus one bar diameter. Hook count can be set to zero, one or two.
Is this the same as a bar bending schedule?
No. This page calculates one shape at a time and explains the formula. A bar bending schedule manages many bars, marks, shape codes, quantities and total steel; use the BBS tool when you need that schedule workflow.
Is the calculator private?
Yes. All calculations run in your browser, and the project state is stored only in your browser local storage. Nothing you enter is uploaded.