Engineering calculators you can check by hand.
Tolerance stacks, cylinders, press fits and bolt torque. Each calculator cites its standard, states its assumptions, shows the working and produces a report you can file.
Calculators
Tolerance stack-up
Worst case, RSS (Bender factor), Monte Carlo
ASME Y14.5-2018, Bender 1962, Fischer 2011
Cylinder force and sizing
Force, speed, regeneration, standard bores, Euler buckling
ISO 3320, ISO 15552, NFPA T3.6.7
Press and interference fit
ISO 286 fits, Lamé pressure and stresses, force, torque, assembly temperature
ISO 286-1/-2, DIN 7190-1
Bolt torque and preload
Nut factor and VDI 2230 thread-geometry torque, preload scatter, thread stress
ISO 898-1, SAE J429, ASTM F3125, VDI 2230
Euler buckling
Euler critical load, slenderness ratio, Johnson parabola, EN 1993-1-1 reduction factor
AISC 360-22, EN 1993-1-1
Thread engagement and stripping
Internal and external thread shear areas, stripping loads, minimum engagement, helical inserts
FED-STD-H28/2B, ISO 965-1, ASME B1.1, ISO 898-1
Stress concentration factor
Kt for shaft shoulders, grooves and holes, peak stress, notch sensitivity and Kf
Peterson's SCF 3rd ed., Roark 8th ed., Shigley 10th ed.
True position
Actual position 2√(dx² + dy²), MMC and LMC bonus, virtual condition, hole patterns, fastener formulas
ASME Y14.5-2018, ISO 1101:2017, ISO 2692:2021
How each calculator is checked
Each method comes from the governing standard first and from recognised textbooks second, and each source is cited with its edition. The aim is an answer a design engineer can defend at a design review.
| Check | What it means |
|---|---|
| Worked examples | Each engine function reproduces a worked example from a cited source, with a number you can check by hand. |
| Automated tests | 903 tests run before any change is published. |
| Show the working | Every result expands to the formulas with your values substituted. |
| Stated limits | Assumptions and the range of validity are listed on each page. |
The full list of worked examples, expected values and computed values is on the validation page. How pages are sourced, reviewed and corrected is in the editorial policy. The calculators are written and reviewed by a practising mechanical design engineer. See about CheckedCalc.
Reference charts
Printable tables computed from the same engines and data as the calculators. Each row opens the calculator with that case loaded, so you can change the friction, preload or grade.
| Chart | Covers |
|---|---|
| Bolt torque charts | All bolt torque and preload charts in one place |
| Metric bolt torque chart | M3 to M36 coarse, ISO 898-1 classes 8.8, 10.9 and 12.9 |
| SAE bolt torque chart | #10 to 1-1/2 in UNC and UNF, SAE J429 Grades 2, 5 and 8 |
| Structural bolt pretension and torque | 1/2 to 1-1/2 in, ASTM F3125 A325 and A490 |
Results are for evaluation and must be verified by a competent engineer before use in a design. See the terms of use.
Latest news
Standard revisions, investigation findings and engineering milestones, each checked against its primary sources.