Convert Kelvin to Reaumur - Temperature Converter

This tool converts a temperature value given in Kelvin (K) to the Réaumur scale (°Ré). The mathematical relationship between these scales is exact; the tool performs the fixed arithmetic conversion and returns the corresponding Réaumur temperature.

Use this converter for quick unit conversions, verification of calculations, or integration into workflows that require Réaumur values. Note that while the numerical conversion is exact, real-world thermometer readings carry measurement uncertainty and potential bias; read the methodology and FAQs for guidance on calibration and accuracy.

Updated Nov 28, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 96ee04060437 • Reviewed by Fidamen Standards Committee

Interactive Converter

Convert between kelvin and reaumur with precision rounding.

Kelvin (K)Reaumur (°Ré)

Quick reference table

Kelvin	Reaumur
1 K	-217.72 °Ré
5 K	-214.52 °Ré
10 K	-210.52 °Ré
25 K	-198.52 °Ré
50 K	-178.52 °Ré
100 K	-138.52 °Ré

Methodology

The conversion uses the defined relationships between Kelvin, Celsius, and Réaumur. Kelvin is an absolute thermodynamic scale where 0 K is absolute zero. Réaumur is a historic scale linked to the Celsius scale by a simple linear factor.

Mathematically the conversion is exact and requires no empirical coefficients. However, when converting measured temperatures (from sensors or instruments) you should account for instrument uncertainty, calibration status, and environmental effects. For traceable measurements, follow calibration and uncertainty practices described by NIST, ISO/IEC 17025, and relevant instrument manufacturer guidance.

Worked examples

Example 1: 273.15 K → (273.15 - 273.15) × 0.8 = 0.00 °Ré (freezing point of water).

Example 2: 373.15 K → (373.15 - 273.15) × 0.8 = 80.00 °Ré (boiling point of water at standard pressure).

Example 3: 300 K → (300 - 273.15) × 0.8 = 21.48 °Ré.

F.A.Q.

Is the conversion exact?

Yes. The mathematical relationship between Kelvin, Celsius, and Réaumur is exact: °Ré = (K - 273.15) × 4/5. Any numerical difference arises from rounding or from uncertainty in the original measured temperature.

Do I need to calibrate my thermometer before converting?

Calibrate instruments according to manufacturer recommendations and accepted standards if you need traceable measurements. Conversion does not remove sensor bias or drift. For traceability and documented uncertainty, use calibration services accredited to ISO/IEC 17025 or national metrology laboratories that provide references to NIST or equivalent.

How should I handle uncertainty?

Report the converted value together with the measurement uncertainty of the original Kelvin reading. Propagate uncertainty through the linear transformation (multiplying uncertainty by 0.8 for Celsius→Réaumur). For formal uncertainty analysis follow the Guide to the Expression of Uncertainty in Measurement (GUM) and relevant NIST/ISO guidance.

Are Réaumur temperatures used in modern practice?

Réaumur is largely historical and rarely used in modern scientific or industrial practice, where Celsius and Kelvin dominate. Use Réaumur only where legacy documents or local conventions require it, and ensure units and tolerances are clearly stated.

Sources & citations

NIST - Temperature and Thermometry — https://www.nist.gov/pml/thermometry
ISO/IEC 17025 - General requirements for the competence of testing and calibration laboratories — https://www.iso.org/standard/66912.html
BIPM - The International System of Units (SI Brochure) — https://www.bipm.org/en/publications/si-brochure
OSHA - Heat Illness Prevention and Workplace Temperature Guidance — https://www.osha.gov/heat-exposure
Guide to the Expression of Uncertainty in Measurement (GUM) — https://www.bipm.org/en/publications/guides
ISO 80000-5:2019 — Thermodynamics — https://www.iso.org/standard/64976.html
NIST SP 330 — The International System of Units (SI) — https://www.nist.gov/pml/special-publication-330

Further resources

Related tools

External guidance

Versioning & Change Control

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

Record ID: 96ee04060437

What changed (latest)

v1.0.0 • 2025-11-28 • 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

Governance

Last updated: Nov 28, 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 • 2025-11-28 • 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: e539062c6282