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Calcimator

Post-Tensioning Calculator

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

Inputs

Results

Total Tendons (both dir)

50

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

How the result changes with Slab Thickness (in)

Slab Thickness (in)Total Tendons (both dir)Elongation (in)
6385.45
11705.45
171075.45
221385.45

What each input means

Slab Length (ft)
Length of the concrete slab
Slab Width (ft)
Width of the concrete slab
Slab Thickness (in)
Thickness of the slab in inches (typical PT slab: 6-10 in)
Superimposed Load (psf)
Total superimposed dead + live load in pounds per square foot

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Slab Length (ft) = 60, Slab Width (ft) = 40, Slab Thickness (in) = 8, Superimposed Load (psf) = 100 = 4 input(s) provided
  2. Calculate Total Tendons
    Total Tendons
    50 = 50
  3. Calculate Elongation
    Elongation
    5.45 = 5.45
  4. Calculate Tendons
    Tendons
    20 = 20
  5. Calculate Tendons
    Tendons
    30 = 30

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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