Coating Adhesion Test Calculator

Calculate pull-off adhesion strength (ASTM D4541) from force, dolly diameter, and specification minimum. Includes pass/fail and statistical analysis.

Inputs

Pull-off force (N)

Dolly diameter (mm)

Spec minimum (MPa)

Number of pulls

Std deviation (MPa)

Tab to move between fields

Results

Adhesion strength (MPa)

2.55

Passes spec (1=yes)

Adhesion strength (psi)369.3

Dolly area (mm²)314.16

Margin vs spec (%)-27.2

Coefficient of variation (%)15.7

95% lower bound (MPa)2.19

Force for spec (N)1,099.6

How to Use This Calculator

Enter the pull-off force recorded by the tester (N), the dolly diameter (mm), and the specification minimum adhesion (MPa).
Enter the number of test pulls and the standard deviation across those pulls for statistical analysis.
Read the adhesion strength in MPa and psi, plus the dolly area, calculated from your inputs.
Check the pass/fail result and the margin versus the specification minimum.
Review the coefficient of variation, the 95% lower confidence bound, and the force needed to meet spec at this dolly size.

How the result changes with Dolly diameter (mm)

Dolly diameter (mm)	Adhesion strength (MPa)	Passes spec (1=yes)
11	8.42	1
36	0.79	0
65	0.24	0
90	0.13	0

What each input means

Pull-off force (N): Maximum force recorded by the adhesion tester in Newtons.
Dolly diameter (mm): Diameter of the test dolly. Standard sizes: 20 mm, 50 mm.
Spec minimum (MPa): Minimum acceptable adhesion per specification. Typical: 1.5–5 MPa.
Number of pulls: Number of test pulls for statistical analysis. ASTM requires ≥ 3.
Std deviation (MPa): Standard deviation across your test pulls (enter from your data).

What each result means

Adhesion strength (MPa): Pull-off strength = Force / dolly area.
Adhesion strength (psi): Same result in pounds per square inch (1 MPa = 145 psi).
Dolly area (mm²): Cross-sectional area of the test dolly.
Passes spec (1=yes): 1 if adhesion ≥ spec minimum, 0 if below.
Margin vs spec (%): How far above (+) or below (−) the specification minimum.
Coefficient of variation (%): CV = std dev / mean × 100. Below 20% is typical for good testing.
95% lower bound (MPa): Lower 95% confidence limit for the mean adhesion.
Force for spec (N): Minimum pull-off force needed to meet specification at this dolly size.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Pull-off force (N) = 800, Dolly diameter (mm) = 20, Spec minimum (MPa) = 3.5, Number of pulls = 5 = 5 input(s) provided
Calculate Adhesion strength
Adhesion strength = forceN / dollyArea
2.55 = 2.55
Calculate Passes spec
Passes spec
0 = 0
Calculate Adhesion strength
Adhesion strength = adhesionMPa * 145.038
369.3 = 369.3
Calculate Dolly area
Dolly area = π * pow(dollyDiameter / 2, 2)
314.16 = 314.16

Engine last updated August 6, 2026. Checked against 3 independently-derived tests — how we verify calculators.

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