Boyle'S Law Calculator

Formula

At constant temperature, final pressure = initial absolute pressure × initial volume ÷ final volume.

Worked example

With Initial absolute pressure: 100 kPa, Initial gas volume: 2 L, Final gas volume: 1.5 L, final absolute pressure is 133.333333 kPa.

Inputs and calculation

Multiply the initial absolute pressure by the original gas volume, then divide by the gas's final volume. This rearranges P₁V₁ = P₂V₂ for the unknown pressure. The displayed relationship is At constant temperature, final pressure = initial absolute pressure × initial volume ÷ final volume. Keep the fields' displayed units attached when reproducing this relationship by hand.

Worked numerical example

For example, enter initial absolute pressure 100 kPa, initial gas volume 2 L, final gas volume 1.5 L. Those inputs produce final absolute pressure of 133.33 kPa.

Holding the other example values fixed, change initial absolute pressure from 100 to 110 kPa. The main output becomes 146.67 kPa. This comparison isolates the effect of that one input.

How to read and use the result

Compressing the gas to a smaller volume increases modeled pressure. The inverse relation holds only while the idealized gas amount and temperature remain fixed. Study an isothermal gas compression or expansion with consistent pressure units.

Practical context

A sealed gas at 100 kPa absolute and 2 L would reach about 133.3 kPa absolute if its volume fell to 1.5 L while temperature stayed constant. The product of pressure and volume is 200 kPa·L in both states. On a pressure gauge that reads relative to atmosphere, 100 kPa gauge is not the same as 100 kPa absolute; the surrounding atmospheric pressure must be added first.

Assumptions and scope

Pressures are absolute, volumes describe the same sealed gas sample, and temperature is constant. Rapid compression may heat a real gas and depart from this isothermal model. Replace the example defaults with measured inputs for your situation and account separately for factors outside these fields.

Checks and common mistakes

Do not enter a gauge pressure without first converting it to absolute pressure. Never use an ideal-gas classroom estimate as a substitute for equipment pressure ratings.

Common questions

What should I verify before using the Boyle'S Law Calculator result?

If compression happens rapidly, the gas may warm and depart from the prediction. When solving the inverse relation, the initial pressure times initial volume must equal the final pressure times final volume. This product is a quick arithmetic check, but agreement does not prove that a real-gas experiment was truly isothermal.