Convert Per Degree Celsius to Per Degree Reaumur
Per Degree Celsius (1/°C) to Per Degree Reaumur (1/°r) coefficient-of-thermal-expansion conversion — enter any value below to get an instant result, or use the table for common values.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
1 1/°C = 1.25 1/°r
1 Per Degree Celsius = 1.25 Per Degree Reaumur
1 Per Degree Reaumur = 0.8 Per Degree Celsius
1 1/°C in every supported unit
Conversion chart: Per Degree Celsius to Per Degree Reaumur
Conversion table
| Per Degree Celsius (1/°C) | Per Degree Reaumur (1/°r) |
|---|---|
| 0.01 1/°C | 0.0125 1/°r |
| 0.1 1/°C | 0.125 1/°r |
| 1 1/°C | 1.25 1/°r |
| 2 1/°C | 2.5 1/°r |
| 3 1/°C | 3.75 1/°r |
| 5 1/°C | 6.25 1/°r |
| 10 1/°C | 12.5 1/°r |
| 20 1/°C | 25 1/°r |
| 50 1/°C | 62.5 1/°r |
| 100 1/°C | 125 1/°r |
| 1000 1/°C | 1250 1/°r |
Per Degree Celsius (1/°C)
Definition: Numerically identical to per-kelvin, since a one-degree-Celsius temperature change is the same size as a one-kelvin change.
History: Used interchangeably with per-kelvin in metric engineering practice, since the Celsius and Kelvin degree are the same size and only differ by a fixed offset that cancels out for an interval-based quantity like expansion.
Current use: Common on European and Asian materials datasheets and engineering handbooks reporting CTE for metals, plastics, glass, and construction materials.
Per Degree Reaumur (1/°r)
Definition: A largely historical thermal expansion unit — since a Reaumur degree represents a larger temperature change (1.25 times a Celsius degree), the coefficient's numeric value is correspondingly smaller.
History: Tied to the historical Reaumur temperature scale used across continental Europe before Celsius became standard, occasionally appearing in older European scientific and engineering literature.
Current use: Now essentially obsolete, encountered only when converting historical European materials data into modern units.
Supported Units
| Unit | Symbol | In Per Kelvin |
|---|---|---|
| Per Kelvin | 1/K | 1 1/K |
| Per Degree Celsius | 1/°C | 1 1/K |
| Per Degree Fahrenheit | 1/°F | 1.8 1/K |
| Per Degree Rankine | 1/°R | 1.8 1/K |
| Per Degree Reaumur | 1/°r | 0.8 1/K |
| PPM per Degree Celsius | ppm/°C | 1E-06 1/K |
About These Parameters
- Value
- The CTE value you want to convert, expressed in the "From" unit. Accepts decimals.
- From Unit
- The CTE unit your input value is currently measured in — most materials datasheets use ppm/°C, while scientific papers often use 1/K.
- To Unit
- The CTE unit you want the result converted into. Use the swap button to flip From and To instantly.
How Thermal Expansion Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to the per-kelvin unit. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Per Degree Celsius → Per Degree Reaumur: multiply by 1.25. For example, 1 1/°C × 1.25 = 1.25 1/°r.
Why Engineers Use Parts Per Million
Real-world coefficients of thermal expansion are tiny — steel expands by roughly 0.000012 of its length per degree Celsius. Written in raw per-kelvin form, that's an awkward number of leading zeros to read and compare across materials. Expressing the same value as "12 ppm/°C" (parts per million) keeps the figure in an easy two-to-three-digit range, which is why virtually every materials datasheet reports CTE in ppm/°C rather than the raw SI unit.
Matching CTE in Joined Materials
When two different materials are bonded, welded, or fitted together — a circuit board and its solder, a filling and a tooth, a coating and its substrate — a large CTE mismatch means the two materials expand and contract at different rates as temperature changes, building up internal stress that can eventually cause cracking or delamination. Engineers use CTE conversion tables like this one specifically to compare candidate materials on a common scale before choosing a combination with closely matched expansion rates.
Example
A CTE of 1 1/°C equals 1.25 1/°r. For scale, structural steel's CTE is about 12 ppm/°C, aluminum's is roughly 23 ppm/°C (almost double), and ordinary glass is around 9 ppm/°C — differences like these are exactly why a glass container can crack when aluminum foil pressed tightly against it heats up faster.
Frequently Asked Questions
How many Per Degree Reaumur are in 1 Per Degree Celsius?
1 Per Degree Celsius (1/°C) equals exactly 1.25 Per Degree Reaumur (1/°r).
Why does this converter use the same math as the Temperature Interval Converter?
Thermal expansion is measured PER degree of temperature change, so its units inherit the same "no offset" property as a temperature interval — a 1/°F coefficient is 1.8 times a 1/°C coefficient for exactly the same reason a Fahrenheit degree of change is 5/9 the size of a Celsius degree of change.
What's a typical CTE value for common materials?
Most structural metals fall between about 10 and 25 ppm/°C — steel around 12, aluminum around 23, copper around 17. Glass and ceramics are typically lower (5-9 ppm/°C), while many plastics run much higher (50-200 ppm/°C), which is why plastic parts need more generous expansion clearances than metal ones.
How accurate are these conversions?
Every conversion factor used here is the exact, internationally recognized relationship between the underlying degree sizes (e.g. 1/°F = exactly 1.8/K) — results are limited only by floating-point display precision, not by rounded conversion constants.