What Is a PSI Calculator?
Pounds per square inch (PSI) is a common unit of pressure used in engineering, automotive, plumbing, and everyday tasks like checking tire inflation. This calculator determines pressure by dividing an applied force, measured in pounds-force (lbf), by the area it acts on, measured in square inches (in²). The result tells you how concentrated that force is over the surface.
How to Use It
Enter the total force in pounds and the contact area in square inches, then read the pressure in PSI. For example, a hydraulic piston pushing with 500 lbf over a 2.5 in² face produces 200 PSI. Make sure both values use the correct units before calculating — mixing units (such as square feet for area) will give incorrect results.
The Formula Explained
The pressure formula is $$P = \frac{F}{A}$$ where P is pressure in PSI, F is force in pounds-force, and A is area in square inches. Because pressure is inversely proportional to area, the same force spread over a larger area produces lower pressure, while a smaller area concentrates the force into higher pressure.
Worked Example
Suppose a flat plate experiences 100 lbf distributed across 4 in². Dividing 100 by 4 gives 25 PSI.
$$\frac{100}{4} = 25 \text{ PSI}$$If the same 100 lbf acted on just 1 in², the pressure would jump to 100 PSI — illustrating how reducing area dramatically increases pressure.
FAQ
What is 1 PSI? One PSI is the pressure resulting from one pound-force applied to one square inch of area.
How do I convert PSI to other units? 1 PSI ≈ 6,894.76 pascals, or about 0.0689 bar. Multiply PSI by these factors to convert.
Can I use this for tire pressure? This computes pressure from raw force and area. Tire gauges report internal pressure directly, but the underlying \(P = \frac{F}{A}\) relationship still applies.
