{"id":470,"date":"2026-07-12T01:43:06","date_gmt":"2026-07-12T01:43:06","guid":{"rendered":"https:\/\/physicsfundamentalsinfo.com\/blog\/?p=470"},"modified":"2026-07-12T01:43:07","modified_gmt":"2026-07-12T01:43:07","slug":"boyles-law","status":"publish","type":"post","link":"https:\/\/physicsfundamentalsinfo.com\/blog\/thermodynamics\/boyles-law\/","title":{"rendered":"Boyle’s Law: Pressure, Volume and the P\u2081V\u2081 = P\u2082V\u2082 Rule"},"content":{"rendered":"\n
Definition<\/div>

\n\nBoyle’s Law states that for a fixed mass of gas at constant temperature, absolute pressure is inversely proportional to volume: pressure times volume stays constant, so P\u2081V\u2081 = P\u2082V\u2082. Halve the volume and the pressure doubles. It is exact for an ideal gas and accurate for real gases at ordinary pressures.\n\n<\/p><\/div>\n\n

Take a breath. Right now, a sheet of muscle under your lungs has pulled downward, your chest cavity has grown by roughly half a litre, and the pressure inside it has dropped about one per cent below the pressure of the room. Air rushed in to close the gap.<\/p>\n\n

You did not pull the air in. You made space, and the atmosphere did the rest. That trade \u2014 more room, less pressure \u2014 is Boyle’s Law, and you have been running it about twenty thousand times a day since the moment you were born.<\/p>\n\n

What Is Boyle’s Law?<\/h2>\n\n

Boyle’s Law says that if you seal a fixed amount of gas in a container and keep its temperature steady, squeezing the gas into a smaller space raises its pressure by exactly the same factor that the volume shrinks. Squeeze it to one-third the volume, and the pressure triples.<\/p>\n\n

Stated formally: at constant temperature, the absolute pressure of a fixed mass of gas is inversely proportional to its volume.<\/strong> “Inversely proportional” is the whole idea in two words. As one goes up, the other goes down, and their product refuses to move.<\/p>\n\n

Three conditions are doing quiet work in that sentence, and every one of them matters:<\/p>\n\n