[ehcrea]

Requested by Eren · project thread

Summary

• New Metric | US segmented switch in the header (shows SI | US on phones). The choice is remembered in the browser (pec:v1:units).
• In US mode every input, result, chart axis, sketch label/caption, PDF report and the material table switch to US customary units, and current values are converted on the spot:
  mm→in, µm/nm→µin, mm²/³/⁴→in²/³/⁴, N→lbf, N/mm & N/µm→lbf/in, Nmm→lbf·in, Nm/rad→lbf·in/rad, Nm²→lbf·in², MPa→ksi, GPa→Msi, kg→lb, kg/m³→lb/in³, mm/s, m/s², m/s³→in/s, in/s², in/s³, K (ΔT)→°F, µm/m·K→µin/in·°F. Angles, time, frequency, g₀ and ratios stay as they are.
• Values are still stored in metric, so saved calculations, JSON files and share links open correctly in either system; typing in US mode converts the entry back to metric.
• Unit mapping lives in US_UNITS in js/core.js; PEC.run now returns result rows in the current system (value stays SI).
• Translations for the new switch in DE/NL/TR.

Tests

• npm test: 805 passed. New checks for conversion factors, results in US mode, and that every sketch in US mode shows no metric units.
• Checked in headless Chromium: switching back and forth, typing in inches, German + US, material table, motion profile charts, PDF export in US units, phone header layout.

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Generated by Claude Code