Make a bar bending schedule (BBS) for a cantilever RCC retaining wall. Enter the wall size and the bars from your structural drawing, and the calculator gives the number and cutting length of every base and stem bar, the steel weight by diameter and the concrete volume. Part of our BBS calculators.
How to use the retaining wall BBS calculator
- Enter the wall length, the stem height above the base, and the base width, depth and toe length.
- Enter the stem thickness at the bottom and the top, and choose the clear cover for the base and the stem.
- Enter the base slab bars: bottom and top, across the width and along the wall.
- Enter the stem bars: vertical and horizontal, on the back (earth) face and the front face.
- If your drawing stops some back-face bars part way up, open Shorter back-face bars and enter them.
- Check the legs and laps, enter the number of identical walls and any wastage, then download the schedule as CSV, print it or share a link.
Retaining Wall BBS Calculator
Bar bending schedule for a cantilever RCC retaining wall: base slab and stem bars, from your drawing
The starting numbers are only a sample. Replace them with the sizes and bars on your structural drawing.
Shorter back-face bars
Legs and laps
Bar bending schedule
Steel by diameter
Checks
Steel quantity only. This tool does not calculate earth pressure, sliding, overturning, bearing pressure or bar sizes. A retaining wall can fail suddenly and needs a geotechnical assessment and a structural design by a licensed engineer. All sizes and bars must come from that drawing.
Formulas used
| Bar | Number | Cutting length |
|---|---|---|
| Base main, across the width | (L − 2cf) ÷ spacing, rounded up, + 1 | B − 2cf + 2 × leg − 2 × 2φ |
| Base distribution, along the wall | (B − 2cf) ÷ spacing, rounded up, + 1 | L − 2cf + 2 × leg − 2 × 2φ, plus laps |
| Stem back face, full height | (L − 2cf) ÷ spacing, rounded up, + 1 | H + in base − cs + bottom L + top L − 2 × 2φ |
| Stem back face, medium or short | (L − 2cf) ÷ spacing, rounded up, + 1 | Bar height + in base + bottom L − 2φ |
| Stem front face, vertical | (L − 2cf) ÷ spacing, rounded up, + 1 | H + in base − cs + bottom L − 2φ |
| Stem horizontal, each face | (H − cs) ÷ spacing, rounded up, + 1 | L − 2cf, plus laps |
L is the wall length, B the base width, H the stem height above the base, cf the base cover, cs the stem cover and φ the bar diameter, all in mm. “In base” is the base depth − base cover − the two bottom bars. Bars longer than 12 m get one 50φ lap for each extra stock bar. Weight is φ² ÷ 162 kg per metre.
Worked example
These are the calculator’s sample values, not a design. A wall 10 m long with a 3000 mm stem, a 2000 × 350 mm base, 50 mm base cover and 40 mm stem cover:
- In base: 350 − 50 − 12 − 10 = 278 mm.
- Base main bars, 12 mm at 150: (10000 − 100) ÷ 150 = 66, + 1 = 67 bars in each layer, 1900 + 400 − 48 = 2252 mm.
- Back-face bars, 12 mm at 150: 67 bars, 3000 + 278 − 40 + 300 + 150 − 48 = 3640 mm.
- Front-face bars, 10 mm at 200: 51 bars, 3000 + 278 − 40 + 300 − 20 = 3518 mm.
- Horizontal bars, 8 mm at 200: (3000 − 40) ÷ 200 = 14.8, rounded up to 15, + 1 = 16 on each face, 9900 mm long.
With the base distribution bars (11 in each layer, 10260 mm long, 10 mm at 200), the total is about 860 kg of steel for 14.5 m³ of concrete.
Frequently asked questions
Does this calculator design a retaining wall?
No. It works out steel quantities from sizes and bars you already have. It does not calculate earth pressure, sliding, overturning, bearing pressure or bar sizes. A retaining wall needs a structural design based on the soil and the height of the retained earth.
Which face of a cantilever retaining wall has the main steel?
The earth-side (back) face. Soil pushes the stem outward, so the back of the stem is in tension and carries the main vertical bars. The front face has lighter bars to control cracking and hold the horizontal steel.
How is the cutting length of a retaining wall stem bar calculated?
A full-height back-face bar is stem height + the depth inside the base − top cover + the bottom L + the top L − 2 × 2φ for the two bends. For a 6000 mm stem with 418 mm inside the base, 30 mm cover, a 300 mm bottom L, a 150 mm top L and 16 mm bars this gives 6774 mm.
Why are some stem bars shorter than others?
Bending in the stem is greatest at the base and falls towards the top, so drawings often stop some of the back-face bars part way up. Enter their heights if your drawing shows them; they are measured from the top of the base.
What cover is used for retaining wall bars?
IS 456 asks for at least 50 mm nominal cover in footings, so the base usually has 50 mm or more. For the stem it gives 30 mm for moderate exposure, which includes concrete in contact with non-aggressive soil, and 45 mm for severe exposure. Follow your drawing.
Does the BBS include weep holes and drainage?
No. Weep holes, drain pipes, filter material and waterproofing are not steel, so they are not in the schedule, but a retaining wall needs them to stop water pressure building up behind it.
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Slab, beam, column, footing and retaining wall schedules.
Disclaimer: Online educational publication only. Not a substitute for structural or geotechnical design by a licensed engineer. Full disclaimer · contact@speakarch.com
Last updated: 8 November 2026