Boyle's Law Calculator
Find final gas pressure at constant temperature.
Results update as you type.
How it works
Boyle's law describes how the pressure of a fixed amount of gas changes when its volume changes at constant temperature, and this calculator finds the resulting final pressure. You enter the initial pressure, the initial volume, and the new volume, and it returns the final pressure. The law states that pressure and volume are inversely proportional: as one goes up, the other goes down, so their product stays constant. Squeeze a gas into half the volume and its pressure doubles; let it expand to twice the volume and its pressure halves. This is one of the fundamental gas laws, discovered by Robert Boyle in the seventeenth century, and it explains everyday phenomena like how a syringe works, why your ears pop with altitude changes, and how the lungs draw in air. It applies when the temperature and the amount of gas stay fixed, so it is a special case of the ideal gas law. The units of pressure and volume can be anything, as long as you use the same units on both sides, since the calculator works with the ratio. Chemistry and physics students, divers, and engineers use it to predict gas behavior. Enter the initial pressure and volume and the final volume to compute the final pressure.
P₁V₁ = P₂V₂ → P₂ = P₁V₁ / V₂
Boyle's law states that for a fixed amount of gas at constant temperature, pressure times volume is constant. So the initial pressure times initial volume equals the final pressure times final volume. Rearranging, the final pressure equals the initial pressure times initial volume divided by the final volume. Pressure and volume are inversely related.
Source:Chemistry (gas laws)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter initial pressure (p₁), initial volume (v₁) and final volume (v₂).
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Final pressure (P₂) updates instantly as you type — no button to press.
Frequently asked questions
What is Boyle's law?
Boyle's law states that, for a fixed amount of gas at constant temperature, the pressure and volume are inversely proportional, so their product stays constant. If volume decreases, pressure increases proportionally, and vice versa. It is a foundational gas law describing how gases respond to compression and expansion at a steady temperature.
How do you calculate final pressure with Boyle's law?
Multiply the initial pressure by the initial volume, then divide by the final volume. This follows from the relationship that initial pressure times initial volume equals final pressure times final volume. Enter your three known values and the calculator returns the final pressure, using consistent units throughout for an accurate result.
What conditions must hold for Boyle's law?
Boyle's law applies only when the temperature and the amount of gas remain constant. If the temperature changes, you need Charles's law or the combined gas law instead, and if the amount of gas changes, the ideal gas law is required. Boyle's law is the constant-temperature special case of these broader laws.
What units should I use?
You can use any units for pressure and volume, such as atmospheres and liters or pascals and cubic meters, as long as you use the same units for both the initial and final values. Because the law works with the ratio of volumes, the units cancel and the final pressure comes out in your chosen pressure unit.
What are everyday examples of Boyle's law?
Boyle's law explains how a syringe draws in fluid when you pull the plunger and increase the volume, why bubbles expand as they rise in water and pressure drops, how the lungs inflate by enlarging the chest cavity, and why scuba divers must manage gas volumes as pressure changes with depth.