Post-Tensioning Calculator

Calculate post-tensioning tendon counts, spacing, elongation, and strand weight for concrete slabs.

Slab Length (ft)

Slab Width (ft)

Slab Thickness (in)

Superimposed Load (psf)

Tab to move between fields

Total Tendons (both dir)

Elongation (in)

5.45

Tendons (length dir)20

Tendons (width dir)30

Approx Spacing (in o.c.)24 in

Force per Tendon (lbs)28,900

Total Strand Weight (lbs)1,248

Slab Area (sq ft)2,400

How to Use This Calculator

Enter the slab length and width in feet and the slab thickness in inches (typical PT slabs are 6–10 in).
Enter the superimposed dead plus live load in psf for your occupancy.
Read Total Tendons (both directions) split into length-direction and width-direction counts.
Use Approx Spacing (in o.c.) to verify your layout fits within typical limits of 48–72 in o.c. for slabs.
Record Elongation (in) — this is the field measurement the stressing crew uses to confirm proper prestress force.
Note Total Strand Weight (lbs) for material ordering and structural dead load calculations.

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