Free tool — Online calculator
Almen Saturation
Curve Calculator
SAE J443 · 10% rule · AMS 2430 / AMS 2432
Your saturation curve,
solved in 30 seconds
Enter the Almen arc heights you measured at different exposure times: the tool fits the saturation curve, derives the saturation time using the SAE J443 10% rule and returns the Almen intensity to declare. Machine, media and parameters must have stayed strictly constant across all points.
Step 1 — Your measured points
At least 3 points, ideally 5 to 8, spread either side of the expected saturation.
Fitted curve
Your results
- Saturation time T
- Declared Almen intensity
- Fitted model
- Goodness of fit (R²)
- Compliance with the 10% rule
Our process experts review your curve, machine parameters and documentation — for audit preparation or process qualification. Answer within 12 working hours.
Have my curve reviewedCalculation method
The tool fits the two-parameter exponential model a(t) = A · (1 − e^(−B·t)), the one most commonly used for saturation curves, by least squares on your points. SAE J443 defines saturation as the earliest point on the curve where doubling the exposure time increases arc height by no more than 10%. With this model that point is exactly T = ln(10)/B, and the corresponding Almen intensity is 0.9 × A. This calculation is a decision aid: it replaces neither your qualified procedure nor sign-off by a process authority.