Consistent base units
Metric and Imperial presentation should resolve to a consistent internal basis so switching display systems does not silently change the job.
Trust through visibility
The calculator should show its working relationship—not ask for blind trust.
BlockToBlock is a planning and estimating aid. It organises checked inputs into useful quantities and costs while keeping professional judgement with the builder.
Visible openings and waste
Deductions and allowances should remain separate, reviewable inputs instead of disappearing inside a result.
Local purchasing reality
Prices, bag sizes, blocks, delivery capacity and supplier units belong to the market where materials are bought.
Conservative rounding
Displayed precision should match the decision. Purchasing quantities may need whole-unit rounding while dimensions retain useful decimals.
Local-first records
Core work should remain usable without a permanent network connection. Backup and future sync must add resilience without obscuring ownership.
Human approval
Imports, suggestions and future AI outputs remain untrusted until a person checks the source and confirms the change.