Case study · Own project · Field-tested tool
Screw calculator
An offline calculator for estimating fixing quantities across seven job types. A working joiner tested it, and their feedback changed both the calculation and the way results are presented.
A practical answer on a phone, even without a connection.
On a job, the useful answer is how many fixings to buy. That means asking for the right measurements, accounting for waste and rounding to boxes. A wall can also need different fixings for its frame and boards, so a single total is not enough.
- 01Job & measurements
- 02Shared calculation engine
- 03Quantities, waste & boxes
What I built
Ask for the job, then the measurements
Different inputs are shown for decking, stud walls, plasterboard, sheet-to-timber, masonry, roofing sheets and metal-to-metal jobs.
Turn a count into a shopping quantity
Results include an adjustable waste allowance and box quantities. Jobs needing different fixings show separate parts, rather than merging them into an unusable total.
Use the units you work in
Metric and imperial inputs feed the same calculation engine. The tool works in a browser and is packaged as an Android app.
Improve it through real feedback
Joiner feedback highlighted missing noggin fixings and their effect on board calculations. Both were corrected and covered by regression tests.
What this delivers
The result is a focused tool that runs offline and explains what to buy. The field-feedback example shows how an apparently small detail in a real workflow can change the underlying calculation.
The technical side
The main components and the decisions behind them.
- App
- Vite and vanilla JavaScript power the web interface. Capacitor packages the same source for Android.
- Calculation design
- Job rules are held separately from the shared engine. Internal measurements use millimetres, with conversions at input and display.
- Verification
- Hand-worked test cases cover job calculations, metric/imperial agreement and the issues found during field feedback.
- Product boundaries
- The calculator estimates quantities for ordering. It leaves anchor selection and structural suitability to the appropriate specifications.
What could this look like for your business?
Your equivalent might be a materials estimator, quote builder, checklist or inspection form. I can turn the rules you use in your work into a tool your team or customers can use consistently.
We can start with a conversation.
You don't need a technical brief. Tell me what you want to make easier, who will use it and what you use now. I'll help work out what needs building.
Talk to me about your idea