Calculate the missing value for pressure difference, loss coefficient, or total pressure drop using any two known inputs in psi, kPa, bar, or Pa.
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Loss Coefficient Formula
The loss coefficient is a unitless ratio between the total pressure drop and the difference in incoming and static pressure. The calculator can solve for any one missing value when you enter the other two.
- K = loss coefficient, unitless
- ΔPt = total pressure drop
- ΔP = difference in incoming and static pressure
To calculate the loss coefficient, the calculator divides total pressure drop by the pressure difference.
To calculate the total pressure drop, it multiplies the pressure difference by the loss coefficient.
To calculate the pressure difference, it divides the total pressure drop by the loss coefficient.
Pressure values can be entered in psi, kPa, bar, or Pa. The calculator converts pressure units internally before applying the formula.
Pressure Unit Conversions Used
These conversion factors are useful when checking the result by hand.
| Unit | To psi | From psi |
|---|---|---|
| psi | 1 psi = 1 psi | 1 psi = 1 psi |
| kPa | 1 kPa = 0.145038 psi | 1 psi = 6.89476 kPa |
| bar | 1 bar = 14.5038 psi | 1 psi = 0.0689476 bar |
| Pa | 1 Pa = 0.000145038 psi | 1 psi = 6894.76 Pa |
Example Problems
Example 1: Find the loss coefficient
You have a total pressure drop of 12 psi and a pressure difference of 4 psi.
The loss coefficient is 3.
Example 2: Find the total pressure drop
You have a pressure difference of 25 kPa and a loss coefficient of 2.4.
The total pressure drop is 60 kPa.
FAQ
Is the loss coefficient unitless?
Yes. The loss coefficient is unitless because it is a ratio of two pressure values. The pressure units cancel out as long as both pressure values are converted to the same unit before division.
Why do the pressure values need matching units?
The formula compares one pressure value to another. If one value is in psi and the other is in kPa, the ratio will be wrong unless you convert them first. The calculator handles this conversion automatically.
Can the loss coefficient be zero?
A loss coefficient of zero means there is no pressure loss in the relationship. In the calculator, it cannot be used when solving for pressure difference because division by zero is not valid.
