Footing Steel Calculator
Enter the footing size, thickness, cover and the bar diameter and spacing each way. The calculator counts the bars in the bottom mesh, works out each cutting length and gives the total steel in kilograms for one footing or several identical ones.
Footing Steel Calculator (BBS)
Planning aid, not a structural design. Footing size, depth, bar sizes and spacing must come from the structural drawings or a qualified structural engineer.
In mm (metric) or inches (imperial); 6 ft also works.
Bar diameter in mm, e.g. 10, 12, 16.
Bar diameter in mm, e.g. 10, 12, 16.
- Total steel
- 44.35 kg
- Steel per footing
- 44.35 kg
- Total bar length
- 49.95 m
44.3 kg of bottom-mesh reinforcement for one footing, before wastage.
How this was calculated
- Effective length = side − 2 × cover
- No. of bars along X = ROUND(effective Y ÷ X-bar spacing + 1); along Y likewise
- Cutting length = effective length + 2 × (D − 2 × cover) − 2 × (2 × dia) (legs turned up, two 90° bends)
- Bar weight = d² ÷ 162.2 kg/m × total length
- Bars along X, Ø12 mm = 12 No. × 2.102 m = 25.22 m × 0.888 kg/m = 22.39 kg
- Bars along Y, Ø12 mm = 13 No. × 1.902 m = 24.73 m × 0.888 kg/m = 21.95 kg
- Total steel = 44.35 kg per footing = 44.35 kg
How to use the footing steel calculator
Enter the footing length X and width Y, its thickness and the clear cover, then the diameter and centre-to-centre spacing of the bars running along X and along Y. If several footings are the same, enter how many.
The effective length each way is the side minus twice the cover. Bars along X are spread across the Y effective length, so their number is effective Y ÷ X-bar spacing + 1, rounded; bars along Y likewise. Each bar is the effective length plus two legs turned up through the footing, each leg the thickness minus both covers, less two 90° bends of 2 × bar diameter each.
What you need from the drawing
Take the footing plan size and depth from the foundation layout, and the bar sizes, spacings and cover from the footing detail. Footings are often given a larger cover than slabs because they sit against soil; use the figure on the drawing.
Accuracy and limitations
The method follows a common site estimating sheet for footing bar bending schedules and with its example inputs gives the same total, 44.35 kg. That sheet reads each bar group’s spacing from the other group’s cell; here each group uses its own spacing, which only matters when the two spacings differ. The schedule covers the bottom mesh only: column starter bars, top mesh and chairs are not included, and neither is wastage. It is a quantity estimate, not a structural design.
Next steps
Use the Pillar Footing Calculator for the concrete and excavation of the same footing, the Steel Quantity Calculator for the column bars that rise from it, and the Slab Steel Calculator for the slabs above.
Frequently asked questions
How is the cutting length of a footing bar worked out?
Cutting length = footing side − 2 × cover + 2 × (thickness − 2 × cover) − 2 × (2 × bar diameter). The middle term adds the two legs turned up at the ends; the last term deducts the two 90° bends.
Why are bars along X counted across the width Y?
Bars that run along X are laid side by side across the footing’s width, so their number depends on the width available (Y minus the covers) and their own spacing.
Does this include the column bars?
No. It covers the bottom mesh of the footing. Use the Steel Quantity Calculator for the column bars, which already allows for the length that goes down into the footing.
How do I get the steel for all the footings in a building?
Run the calculator once for each footing type, with the number of identical footings of that type, and add the totals.
Ready to plan your space?
It is free, runs in your browser and needs no account. Projects are saved privately on this device.