The CUP ↔ PSI Calculator helps convert pressure measurements between Copper Units of Pressure (CUP) and Pounds per Square Inch (PSI). These pressure units are commonly used in ballistics and ammunition testing to measure the chamber pressure of firearms.
CUP is an older method of measuring pressure, relying on the compression of a copper cylinder under the force of gas expansion in a firearm chamber. PSI, on the other hand, is a more modern and precise measurement obtained through electronic pressure sensors. Since the two units measure similar concepts but are derived using different methods, a conversion formula is necessary for accuracy.
This calculator is useful for firearm enthusiasts, ammunition reloaders, and ballistic engineers who need to compare or standardize pressure values across different testing methods.
Formula of CUP ↔ PSI Calculator
To convert between CUP and PSI, use the following formulas:
Formula to convert CUP to PSI:
PSI = (CUP × 1.516) - 17,902
Where:
- CUP is the pressure in Copper Units of Pressure
- PSI is the pressure in Pounds per Square Inch
Formula to convert PSI to CUP:
CUP = (PSI + 17,902) / 1.516
Where:
- PSI is the pressure in Pounds per Square Inch
- CUP is the pressure in Copper Units of Pressure
These formulas provide a close approximation, though slight variations may occur due to differences in measurement techniques and specific testing conditions.
General CUP to PSI and PSI to CUP Conversion Table
The table below provides estimated conversions between CUP and PSI for common values:
| CUP (Copper Units of Pressure) | PSI (Pounds per Square Inch) |
|---|---|
| 20,000 | 12,418 |
| 25,000 | 19,998 |
| 30,000 | 27,578 |
| 35,000 | 35,158 |
| 40,000 | 42,738 |
| 45,000 | 50,318 |
| 50,000 | 57,898 |
This reference helps users quickly estimate pressure values without manually calculating them.
Example of CUP ↔ PSI Calculator
Suppose you have a pressure measurement of 35,000 CUP and want to convert it to PSI.
- Use the formula:
PSI = (CUP × 1.516) - 17,902
PSI = (35,000 × 1.516) - 17,902
PSI = 35,158
This means that 35,000 CUP is approximately equal to 35,158 PSI.
If you want to convert 42,000 PSI to CUP:
- Use the formula:
CUP = (PSI + 17,902) / 1.516
CUP = (42,000 + 17,902) / 1.516 = 39,635
This means that 42,000 PSI is approximately equal to 39,635 CUP.
Most Common FAQs
CUP (Copper Units of Pressure) is an older method that uses the deformation of a copper cylinder to estimate chamber pressure. PSI (Pounds per Square Inch) is a more precise measurement obtained using electronic pressure sensors. CUP values are typically lower than PSI values for the same pressure because the methods used to measure them are different.
CUP was traditionally used before electronic pressure sensors became widely available. Some ammunition manufacturers still report pressure in CUP, especially for older cartridges. However, PSI has become the industry standard due to its higher accuracy and consistency across different measurement conditions.
CUP and PSI values are not directly interchangeable because they are measured differently. The conversion formulas provide an estimate, but it is always best to use the specific pressure data recommended for a particular firearm or ammunition type to ensure safety.