References & further reading

• BIPM SI Brochure for SI base and derived units.
• NIST SP 811 on expressing uncertainty and significant digits (mirrored by the precision slider).
• ISO 80000 series for quantities and units—conceptual alignment for stress as pressure-type quantity.
• IEC 60050 for rotational machinery vocabulary (rpm as conventional rotation rate).

Legacy engineering units & literature lineage

• The registry includes P0/P1 legacy units commonly found in pre-SI heat-transfer and chemical-engineering handbooks—e.g. kcal/(m²·h·°C), cal/(cm²·s·°C), cal/(cm·s·°C), kcal/(kg·°C), CHU, kg/(m·h), dyn, poundal, erg, kgf·m (work), kcal/s, inHg, lb/gal(US), US short ton, and oil barrel (42 US gal).
• Numeric factors are derived from NIST/ISO definitions (g = 9.80665 m/s², IT calorie 4.1868 J, IT BTU 1055.05585262 J, 1959 inch definition, etc.) and computed with decimal.js—not copied from four-digit tables in older printed references.
• Literature lineage: many heat-exchanger workflows still cite Obana, Heat Exchanger Design Handbook (1974 JP / 1982 CN translation, Petroleum Industry Press). That appendix motivated unit coverage; the handbook is not the numeric SSOT when it disagrees with modern constants.
• Surface tension now includes handbook/SysCAD units kg/m (kgf/m), g/cm (gf/cm), N/cm, N/mm, lb/ft; selecting kg/m shows a one-time note that it is not mass/length.
• Belt line rating covers SI N/m and legacy catalogue units kg/cm (kgf/cm), kg/m (kgf/m), lbf/in (DTII(A)/CEMA)—allowable tension per belt width, distinct from surface tension despite shared N/m dimension.
• Temperature deltas in heat-transfer coefficients use °C or K interchangeably for ΔT (same numeric increment); anchors remain SI (W/(m²·K), W/(m·K), J/(kg·K)).
• Intentionally excluded niche units from the same tables: Japanese shaku/kan, Chinese dan (石), the obsolete Chinese glyph for kilowatt (瓩), and duplicate “kg (mass)” labels—use kg, kgf, or Pa·s instead.
• When reconciling with Excel or a scanned handbook table, expect small differences: handbook rounding, 15 °C vs thermochemical calories, or mixed kgf/kg force notation in old prose.

Model assumptions

• Linear factors only (except temperature, which uses offsets in its own category). Values follow (value × factor_to_SI_anchor) / factor_target.
• Rotational speed: rpm and rev/s map to rad/s via 2π; °/s maps via π/180.
• Stress category uses the same pascal definition as pressure but is listed separately to avoid mixing operating pressure with material strength in workflows.
• Plane angle: °, arcmin, and arcsec convert to rad via π/180; listed separately from rotational speed (°/s) and from thermodynamic temperature (°C).

Shareable URL

When the toolbar exposes “Copy shareable link”, inputs can be encoded in the URL so colleagues can reopen the same case. All computations run locally in your browser; this tool may not expose share links yet.