Crack Width & Deflection Calculator
Serviceability (SLS) check for a reinforced-concrete beam or one-way slab strip: flexural crack width and long-term deflection by the curvature method (creep + shrinkage). Un-factored quasi-permanent actions, per-check utilisation, and a printable clause-by-clause calc sheet.
Crack width per BS 8110-2 & EN 1992-1-1 cl 7.3; deflection by the curvature method per BS 8110-2 / EN 7.4
Inputs
Element
Design code
Span & support
m
Loads (characteristic, un-factored)
kN/m
kN/m
Section geometry
mm
mm
mm
mm
Tension reinforcement
mm
mm
mm
As = — mm²
Compression reinforcement (optional)
mm
mm
As′ = — mm²
n'=0 (default) disables the compression-steel correction entirely — matches the tension-only formulas exactly.
Materials
MPa
Deflection limits
Creep, shrinkage & duration
µε
Element
Deflected shape
Serviceability result
—
—
enter data
| SLS load w | — |
| Service moment M | — |
| Ecm / Ec,eff | — |
| Cracking moment Mcr | — |
| Distribution ζ | — |
| Crack width | — |
| Flexural + shrinkage defl. | — |
| Total long-term defl. | — |
Cracked section
Serviceability checks
Step-by-step calculation
This isn't a toy calculator
It shares the STATIX engine — a full structural suite built on the same engine. Model the whole building, not just one member.