Rebar Lap Length Calculator

Inputs

Results update as you type.

Code & bar
Materials & conditions
Lap spliceLap in tension 777 mm777 mmcompression 621 mm · 48.5 × dbmyconstructioncalculator.comNot to scale
Diagram updates as you type.

Results

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Lap length in tension
777mm
In bar diameters48.5 × db
Lap length in compression621 mm
Compression in bar diameters38.8 × db
Development length (tension)777 mm

Uses the simplified code equations. Your structural drawings and the engineer of record govern: they may specify longer laps, different splice classes, or seismic detailing.

Stagger laps where possible, and do not lap bars larger than #11 / 36 mm in tension (ACI) or 36 mm (IS): use couplers.

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Working
  1. τbd (M25) = 1.40 N/mm² × 1.6 (deformed bars) = 2.24 N/mm²
  2. Ld = φ × 0.87 fy ÷ (4 τbd) = 16.0 × 0.87 × 500 ÷ (4 × 2.24) = 777 mm (48.5 φ)
  3. Compression: τbd × 1.25 → Ld = 621 mm (38.8 φ)
  4. Tension lap = max(Ld, 30φ) = 777 mm
  5. Compression lap = max(Ld compression, 24φ) = 621 mm

Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.

Rebar Lap Length Calculator byMy Construction Calculator: free construction calculators with the working shown.