Bar Bending Schedule (BBS) Calculator

What is a bar bending schedule?

A bar bending schedule (BBS) is a table that lists every reinforcing bar in a structure by mark, with its diameter, shape, dimensions, quantity, cutting length and weight. The fabricator cuts and bends from it and the buyer takes the tonnage from it.

How is cutting length calculated?

The cutting length is the straight length of the bar before bending. Add up the outside to outside dimensions of the shape:

• Straight bar: L = A
• L shape: L = A + B
• U shape: L = A + B + C
• Closed stirrup: L = 2 × (A + B) + 2 × hook length

A bar stretches a little at each corner when it is bent. Fabricators therefore deduct a small amount per bend that depends on the bar diameter. How much depends on the standard in use and on the shop. In this tool the deduction factor is your input. Left at zero, the length is on the safe side and slightly long.

Example

Ten L bars of 12 mm with legs of 3.20 m and 0.25 m. Without deduction the cutting length is 3.45 m. Deducting 2 bar diameters per 90 degree bend gives 3.45 − 2 × 0.012 = 3.426 m. The total length is 34.26 m and the weight 34.26 × 0.888 = 30.4 kg.

Weight

Mass per metre is π / 4 × d² × 7850 with d in metres. Total weight is cutting length times quantity times mass per metre. The summary by diameter shows how many tonnes of each size to order.

How to use it

Add one row per bar mark, choose the diameter and the shape, then enter the dimensions and the quantity. The schedule can be downloaded as CSV or printed. It is stored in your browser, so it survives closing the page.

Limits

This is a quantity tool, not a design tool. It knows four basic shapes only. Lap lengths, hook lengths and bend deductions are yours to set. Bars longer than 12 metres are flagged, but the tool does not choose splice positions.