Software for hardware.
Datumio is a set of 19 interactive engineering calculators for the hand calculations hardware engineers actually do — press fits, bolted joints, foam gaskets, springs, thermal stacks, tolerance analysis. Every input is a slider, every output updates in real time, and every calculator draws what it computes.
The textbook formulas haven't changed in fifty years. What's changed is that they can now be instruments instead of spreadsheet cells: drag a shaft diameter and watch the interference pressure climb; drag a spec limit onto a Monte Carlo distribution and watch the yield move. The goal is that the calculation you'd normally re-derive on a whiteboard is one URL away, already checked, already drawn.
Every formula is implemented from a published reference, and every implementation ships with hand-computed test vectors that run in CI. When a model makes a simplifying assumption, the assumption is stated on the calculator — not buried. Where a result is an empirical estimate rather than physics, the tooltip says so.
| Reference | Used for |
|---|---|
| Shigley's Mechanical Engineering Design | Press fits, springs, bolted joints, beams |
| Roark's Formulas for Stress and Strain | Beam stress and deflection |
| VDI 2230 | Bolted joint preload and tightening torque |
| Machinery's Handbook, FED-STD-H28/2B, ISO 898-1 | Thread engagement length and stripping strength |
| ASTM D3574, Rogers CFD | Foam compression and gasket sealing force |
| Parker O-Ring Handbook (ORD 5700), SAE AS568 | O-ring gland squeeze, fill, stretch and extrusion gap |
| BASF / Bayer snap-fit design guides | Snap-fit cantilever beams |
| IPC-2221A (§6.2 conductor sizing), IEC 60028 copper resistivity | PCB trace resistance and temperature rise |
| Holm, Electric Contacts: Theory and Application | Spring-contact constriction resistance and contact heating |
| JEDEC JESD51-2A / JESD51-12 | Package thermal metrics (θJA, θJC, ΨJT) behind the junction temperature chain |
| NIST Engineering Statistics Handbook, Drake (1999) | Tolerance stack-up methods |
The roadmap is driven by requests from working engineers. Tell us what you re-derive most often: [email protected]. See pricing for what's in the free and Pro tiers.