Fidamen

Convert Rankine to Reaumur - Temperature Converter

This converter translates a temperature value on the Rankine scale (absolute scale based on Fahrenheit degrees) into the Réaumur scale (an older centigrade-related scale where 0°Ré is freezing and 80°Ré is boiling of water at standard pressure). Use this for historical data, conversions in legacy engineering texts, or academic work.

Results are computed using an exact fixed relationship between the scales via Kelvin/Celsius intermediates. For traceable measurement work, follow calibration and uncertainty guidance below and consult the cited standards for recommended procedures and reporting.

Values are returned as exact mathematical results; for reporting, round to the precision appropriate for your measurement context and record estimates of uncertainty if the input originates from instruments.

Updated Nov 14, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 8980892b1d20 • Reviewed by Fidamen Standards Committee

Interactive Converter

Convert between rankine and reaumur with precision rounding.

Quick reference table

RankineReaumur
1 °R-218.08 °Ré
5 °R-216.3 °Ré
10 °R-214.08 °Ré
25 °R-207.41 °Ré
50 °R-196.3 °Ré
100 °R-174.08 °Ré

Methodology

Conversion is performed by translating Rankine to Kelvin (or Celsius) then converting Celsius to Réaumur. This preserves the fixed ratios between degree sizes and absolute-zero offsets.

We present both the stepwise method and the consolidated linear formula. The method aligns with SI referencing practices and traceability recommendations from measurement authorities.

For measurement-grade work, apply instrument calibration data and include uncertainty budgets following guidance from NIST and ISO metrology standards cited below.

Key takeaways

Use the linear formula °Ré = (4/9) × °R − 218.52 for direct Rankine to Réaumur conversion.

For laboratory or regulatory use, include calibration status and propagated uncertainty and consult the cited NIST and ISO documents for traceability requirements.

Worked examples

Convert 671.67 °R (steam at water boiling point, standard pressure): °Ré = (4/9)*671.67 − 218.52 = 80.00 °Ré.

Convert 0 °R (absolute zero): °Ré = (4/9)*0 − 218.52 = −218.52 °Ré, which corresponds to −273.15 °C.

Convert 491.67 °R (equivalent to 32 °F, freezing point of water): °Ré = (4/9)*491.67 − 218.52 = 0.00 °Ré.

F.A.Q.

What symbols are used for these scales?

Rankine is commonly denoted °R or °Ra. Réaumur is denoted °Ré or °Re. Be explicit when reporting to avoid symbol confusion with other scale abbreviations.

How precise is the converter and how should I round results?

The mathematical conversion is exact for real-number arithmetic. Round to a number of decimal places that matches the input measurement precision or instrument uncertainty. For laboratory reporting, follow significant-figure rules and include uncertainty estimates.

Are there limits or common pitfalls?

Réaumur is a historical scale and rarely used for modern instrumentation. Watch for mislabelled degrees (e.g., confusing °R with °Ré). Also note that Réaumur is most meaningful near typical laboratory temperatures; for extreme values, document physical relevance and instrument calibration status.

Do I need to calibrate instruments before using these conversions?

Yes. For any measurement used as input, ensure the thermometer or sensor has current calibration traceable to national standards. Follow calibration intervals and uncertainty estimation methods recommended by NIST and ISO metrology guidance.

How should I report uncertainty after conversion?

Propagate input measurement uncertainty through the linear conversion formula. For a conversion y = a*x + b, the absolute uncertainty is |a| times the input uncertainty. Document the method used for propagation and reference standards used for calibration and uncertainty evaluation.

Sources & citations

Further resources

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: 8980892b1d20

What changed (latest)

v1.0.0 • 2025-11-14 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Public QA status

PASS — golden 25 + edge 120

Last run: 2026-01-23 • Run: golden-edge-2026-01-23

Engine

v1.0.0

Data

Baseline (no external datasets)

Content

v1.0.0

UI

v1.0.0

Governance

Last updated: Nov 14, 2025

Reviewed by: Fidamen Standards Committee (Review board)

Credentials: Internal QA

Risk level: low

Reviewer profile (entity)

Fidamen Standards Committee

Review board

Internal QA

Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person

Semantic versioning

  • MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
  • MINOR: New features or fields that do not change existing outputs for the same inputs.
  • PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.

Review protocol

  • Verify formulas and unit definitions against primary standards or datasets.
  • Run golden-case regression suite and edge-case suite.
  • Record reviewer sign-off with credentials and scope.
  • Document assumptions, limitations, and jurisdiction applicability.

Assumptions & limitations

  • Uses exact unit definitions from the Fidamen conversion library.
  • Internal calculations use double precision; display rounding follows the unit's configured decimal places.
  • Not a substitute for calibrated instruments in regulated contexts.
  • Jurisdiction-specific rules may require official guidance.

Change log

v1.0.0 • 2025-11-14 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: 1bc74676c705