Thermal Expansion Converter
Convert between coefficient-of-thermal-expansion (CTE) units — per kelvin, ppm per degree Celsius, per Fahrenheit, per Rankine, and per Reaumur.
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
12 ppm/°C = 6.66667E-06 1/°F
1 PPM per Degree Celsius = 5.55556E-07 Per Degree Fahrenheit
1 Per Degree Fahrenheit = 1800000 PPM per Degree Celsius
12 ppm/°C in every supported unit
What is a Thermal Expansion Converter?
The coefficient of thermal expansion (CTE) describes how much a material's length changes for every degree of temperature change — it's why railway tracks have small gaps, bridges have expansion joints, and glass cookware can crack under sudden heat. This converter translates a CTE reading from one unit into another, so a materials datasheet in ppm/°C, a scientific paper in 1/K, and a US engineering spec in 1/°F can all be compared directly.
Every unit here is a rate — a fractional length change PER degree — so they're all defined relative to the SI per-kelvin unit by a fixed multiplier, with no offset involved (the same reason the site's Temperature Interval Converter is purely linear rather than needing the Celsius/Fahrenheit offset).
Conversion chart: PPM per Degree Celsius to Per Degree Fahrenheit
Conversion table
| PPM per Degree Celsius (ppm/°C) | Per Degree Fahrenheit (1/°F) |
|---|---|
| 0.01 ppm/°C | 5.55556E-09 1/°F |
| 0.1 ppm/°C | 5.55556E-08 1/°F |
| 1 ppm/°C | 5.55556E-07 1/°F |
| 2 ppm/°C | 1.11111E-06 1/°F |
| 3 ppm/°C | 1.66667E-06 1/°F |
| 5 ppm/°C | 2.77778E-06 1/°F |
| 10 ppm/°C | 5.55556E-06 1/°F |
| 20 ppm/°C | 1.11111E-05 1/°F |
| 50 ppm/°C | 2.77778E-05 1/°F |
| 100 ppm/°C | 5.55556E-05 1/°F |
| 1000 ppm/°C | 0.00055555556 1/°F |
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 PPM per Degree Celsius → Per Degree Fahrenheit: multiply by 5.55556E-07. For example, 12 ppm/°C × 5.55556E-07 = 6.66667E-06 1/°F.
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 12 ppm/°C equals 6.66667E-06 1/°F. 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
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.