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Fatigue Life Estimator

Calculate Basquin life, two-point S-N curve coefficients, Goodman/Gerber/Soderberg corrections, and Miner damage for preliminary fatigue review.

Fatigue Life inputs

Calculations are performed locally in your browser and are not submitted to a third-party calculation API.

Calculation mode

Display precision

Material properties

Material property mode

Material preset

Young's modulus

Young's modulus unit

Shear modulus

Shear modulus unit

Yield strength

Yield strength unit

Ultimate strength

Ultimate strength unit

Generic steel values. Use grade-, standard-, temperature-, and process-specific data for real design.

Fatigue stresses and life data

Mean-stress correction

Stress output unit

Maximum stress

Maximum stress unit

Minimum stress

Minimum stress unit

Stress amplitude

Stress amplitude unit

Basquin coefficient A

Basquin coefficient A unit

Basquin exponent b

S-N cycles 1

S-N stress 1

S-N stress 1 unit

S-N cycles 2

S-N stress 2

S-N stress 2 unit

Miner cycles 1

Miner life 1

Miner cycles 2

Miner life 2

Result section

warningmean-stress

Mean-stress corrected amplitude

62.5 MPa

Secondary results

Estimated Basquin life: 7.42496e+12 cycles
Stress amplitude: 50 MPa
Mean stress: 100 MPa
Stress ratio R: 0.333333
Corrected equivalent amplitude: 62.5 MPa
Basquin coefficient A: 900 MPa
Basquin exponent b: -0.09
Miner cumulative damage: 0.5
Repeat blocks to unit damage: 2

Unit conversion summary

Unit-normalization summary: 5.00000e+7 Pa; 1.00000e+8 Pa; 6.25000e+7 Pa

Warnings

Calculations are performed locally in your browser and are not submitted to a third-party calculation API.
Material properties vary with grade, condition, temperature, manufacturing process, loading direction, heat treatment, applicable standard, and data source. Verify all properties for the actual material.
These calculations are preliminary scalar mechanics checks and do not certify design adequacy.
No fatigue curve is inferred from material name. No rainflow counting, crack growth, weld class, or reliability model is included.

Assumptions

User-entered S-N data represents the actual material, surface, size, environment, and loading direction.
Miner damage is linear cumulative damage and does not perform cycle counting.

Calculation steps

Resolve cyclic stress5.00000e+7 Pa
Apply mean-stress correctiongoodman: 6.25000e+7 Pa
Resolve S-N curveA=9.00000e+8 Pa, b=-0.09
Calculate life7.42496e+12 cycles
Calculate Miner damage0.5

Basquin S-N and mean-stress correction

N=(sigma_a/A)^(1/b); D=sum(n_i/N_i)

sigma_a = A N^b; N = (sigma_a/A)^(1/b); Goodman, Gerber, and Soderberg adjust alternating stress for mean stress.

sigma_a,eq = 6.25000e+7 Pa

N = (6.25000e+7 Pa / 9.00000e+8 Pa)^(1 / -0.09)

Technical visual

Engineering interpretation

Fatigue estimates are sensitive to local stress, detail category, material data, and scatter. Treat results as screening values only.

What is the fatigue life estimator?

This estimator performs basic stress-life fatigue calculations from user-entered S-N data. It reports alternating stress, mean stress, corrected equivalent amplitude, Basquin life, and Miner damage for simple load blocks.

How to use the fatigue life estimator

Choose the fatigue calculation mode that matches the hand calculation you want to perform.
Enter geometry, loads, material values, and units from a consistent source.
Review the primary result, secondary values, formula substitution, assumptions, and warnings.
Use the related-tool links only as a workflow aid; verify every transferred value before design use.

Input explanations

Use measured, tested, or verified S-N data for the actual material and condition.
Mean-stress correction requires appropriate ultimate or yield strength input.
Miner damage uses entered cycles and entered lives; it does not perform rainflow counting.
Stress units are converted to SI internally before calculating life.
Material properties vary with grade, condition, temperature, manufacturing process, loading direction, heat treatment, applicable standard, and data source. Verify all properties for the actual material.

Notation

Formula notation
Symbol	Meaning	Unit
sigma_a	Alternating stress amplitude	Pa
sigma_m	Mean stress	Pa
N	Cycles to failure estimate	cycles
A, b	Basquin coefficient and exponent	Pa, -
D	Miner cumulative damage	-

Worked examples

Goodman correction for sigma_a = 100 MPa, sigma_m = 50 MPa, and Sut = 500 MPa gives 111.111 MPa.

Gerber correction for the same values gives about 101.010 MPa.

Miner blocks with damages 0.2 and 0.3 give total damage 0.5 and two repeat blocks to unit damage.

Cross-tool workflow

The fatigue workflow can consume stress amplitudes from shaft, weld, or FEA stress calculators, but it does not create material fatigue data.

Use shaft stress workflow Use weld stress workflow

Common mistakes

Inventing fatigue curves from a material name.
Using peak stress where alternating stress is required.
Ignoring stress concentrations, surface finish, size effects, environment, weld class, and reliability factors.
Treating Miner damage as exact failure prediction.

Limitations

No rainflow counting, crack growth, notch correction, weld class, or probabilistic reliability model.
S-N coefficients must be supplied by the user.
Mean-stress corrections are simplified scalar models.

References

Shigley's Mechanical Engineering Design: Budynas and Nisbett, Shigley's Mechanical Engineering Design.
Mechanics of Materials: Common mechanics-of-materials texts covering torsion, beam deflection, column buckling, and elastic stress relationships.
NIST SP 811: NIST Special Publication 811, Guide for the Use of the International System of Units.

What is an S-N curve?

An S-N curve relates cyclic stress amplitude to cycles to failure for a material, detail, and test condition.

What is alternating stress?

Alternating stress is half the difference between maximum and minimum cyclic stress.

Goodman versus Gerber?

Goodman is linear and often conservative; Gerber is parabolic and less conservative for ductile metals.

What is Miner's rule?

Miner's rule sums cycle ratio damage n_i/N_i across blocks as a linear damage estimate.

Is estimated fatigue life guaranteed?

No. Fatigue scatter and detail effects are large; verify with applicable data, testing, and professional review.

Does the tool include stress concentration?

No. Enter a corrected local stress amplitude when concentration effects matter.

Does the tool create material curves?

No. It only uses user-entered fatigue data.

Professional support from ScholarEase Consultancy Services LLP

Professional FEA, simulation setup, solid-mechanics calculations, mechanical-design review, technical documentation, and research support are available through the connected services website. These calculators remain free to use without purchasing services.

Visit ScholarEase

Engineering disclaimer

This tool is intended for educational, estimation, and preliminary engineering use. It does not certify designs or replace applicable codes, standards, validated software, physical testing, or qualified professional engineering judgment.

Need Professional Support?

ScholarTool is powered by ScholarEase Consultancy Services LLP. Professional engineering, simulation, research, and technical documentation support is available through the connected services website.

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Last reviewed: 2026-06-30

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Fatigue Life inputs

Calculations are performed locally in your browser and are not submitted to a third-party calculation API.

Calculation mode

Display precision

Material properties

Material property mode

Material preset

Young's modulus

Young's modulus unit

Shear modulus

Shear modulus unit

Yield strength

Yield strength unit

Ultimate strength

Ultimate strength unit

Generic steel values. Use grade-, standard-, temperature-, and process-specific data for real design.

Fatigue stresses and life data

Mean-stress correction

Stress output unit

Maximum stress

Maximum stress unit

Minimum stress

Minimum stress unit

Stress amplitude

Stress amplitude unit

Basquin coefficient A

Basquin coefficient A unit

Basquin exponent b

S-N cycles 1

S-N stress 1

S-N stress 1 unit

S-N cycles 2

S-N stress 2

S-N stress 2 unit

Miner cycles 1

Miner life 1

Miner cycles 2

Miner life 2

Result section

warningmean-stress

Mean-stress corrected amplitude

62.5 MPa

Secondary results

Estimated Basquin life: 7.42496e+12 cycles
Stress amplitude: 50 MPa
Mean stress: 100 MPa
Stress ratio R: 0.333333
Corrected equivalent amplitude: 62.5 MPa
Basquin coefficient A: 900 MPa
Basquin exponent b: -0.09
Miner cumulative damage: 0.5
Repeat blocks to unit damage: 2

Unit conversion summary

Unit-normalization summary: 5.00000e+7 Pa; 1.00000e+8 Pa; 6.25000e+7 Pa

Warnings

Calculations are performed locally in your browser and are not submitted to a third-party calculation API.
Material properties vary with grade, condition, temperature, manufacturing process, loading direction, heat treatment, applicable standard, and data source. Verify all properties for the actual material.
These calculations are preliminary scalar mechanics checks and do not certify design adequacy.
No fatigue curve is inferred from material name. No rainflow counting, crack growth, weld class, or reliability model is included.

Assumptions

User-entered S-N data represents the actual material, surface, size, environment, and loading direction.
Miner damage is linear cumulative damage and does not perform cycle counting.

Calculation steps

Resolve cyclic stress5.00000e+7 Pa
Apply mean-stress correctiongoodman: 6.25000e+7 Pa
Resolve S-N curveA=9.00000e+8 Pa, b=-0.09
Calculate life7.42496e+12 cycles
Calculate Miner damage0.5

Basquin S-N and mean-stress correction

N=(sigma_a/A)^(1/b); D=sum(n_i/N_i)

sigma_a = A N^b; N = (sigma_a/A)^(1/b); Goodman, Gerber, and Soderberg adjust alternating stress for mean stress.

sigma_a,eq = 6.25000e+7 Pa

N = (6.25000e+7 Pa / 9.00000e+8 Pa)^(1 / -0.09)

How to use the fatigue life estimator

Choose the fatigue calculation mode that matches the hand calculation you want to perform.
Enter geometry, loads, material values, and units from a consistent source.
Review the primary result, secondary values, formula substitution, assumptions, and warnings.
Use the related-tool links only as a workflow aid; verify every transferred value before design use.

Input explanations

Use measured, tested, or verified S-N data for the actual material and condition.
Mean-stress correction requires appropriate ultimate or yield strength input.
Miner damage uses entered cycles and entered lives; it does not perform rainflow counting.
Stress units are converted to SI internally before calculating life.
Material properties vary with grade, condition, temperature, manufacturing process, loading direction, heat treatment, applicable standard, and data source. Verify all properties for the actual material.

Symbol

Meaning

Unit

sigma_a

Alternating stress amplitude

sigma_m

Mean stress

Cycles to failure estimate

cycles

A, b

Basquin coefficient and exponent

Pa, -

Miner cumulative damage

References

Shigley's Mechanical Engineering Design: Budynas and Nisbett, Shigley's Mechanical Engineering Design.

Mechanics of Materials: Common mechanics-of-materials texts covering torsion, beam deflection, column buckling, and elastic stress relationships.

NIST SP 811: NIST Special Publication 811, Guide for the Use of the International System of Units.

Fatigue Life inputs

Calculation mode

Material properties

Fatigue stresses and life data

Result section

Secondary results

Unit conversion summary

Warnings

Assumptions

Calculation steps

Basquin S-N and mean-stress correction

Technical visual

Engineering interpretation

What is the fatigue life estimator?

How to use the fatigue life estimator

Input explanations

Notation

Worked examples

Cross-tool workflow

Common mistakes

Limitations

References

Related tools

Professional support from ScholarEase Consultancy Services LLP

Print summary

Engineering disclaimer

Need Professional Support?

Fatigue Life inputs

Calculation mode

Material properties

Fatigue stresses and life data

Result section

Secondary results

Unit conversion summary

Warnings

Assumptions

Calculation steps

Basquin S-N and mean-stress correction

Technical visual

Engineering interpretation

What is the fatigue life estimator?

How to use the fatigue life estimator

Input explanations

Notation

Worked examples

Cross-tool workflow

Common mistakes

Limitations

References

Related tools

Professional support from ScholarEase Consultancy Services LLP

Print summary

Engineering disclaimer

Need Professional Support?