Combined gas law final pressure calculator

This capacity rearranges P1 V1 over T1 equals P2 V2 over T2 to compute P2 equals P1 times V1 times T2 over V2 times T1 deterministically, rejects zero final volume with a clear invalid_input error, and returns structured JSON with both states, the formula, the method label, and a fixed-amount flag.

What the combined gas law means and which quantities you need to send

Delivering p1, v1, t1, v2, t2, p2, formula, method, and amount as JSON makes the result easy to paste into notes, diff in automated tests, or reuse across languages without reimplementing the multiply-and-divide arithmetic. Keep pressure units consistent between the initial and final states and keep volume units consistent as well; the engine does not convert atmospheres to kilopascals, liters to cubic meters, or Celsius to kelvin for you, so convert to absolute kelvin before calling and use the same pressure and volume families for P1 with P2 and V1 with V2 throughout the request body.

How this calculator validates input and applies P2 = P1 · V1 · T2 / (V2 · T1)

Numeric strings that parse to finite numbers are accepted so forms and CSV-style pipelines can pass values without an extra cast. Pressures and volumes must be positive as well. There is no Boyle-only isothermal branch, no Charles-only isobaric branch, no Gay-Lussac-only isochoric branch, no amount-of-substance term, and no unit conversion service; this is pure combined gas law for final pressure at fixed amount. Send a JSON body with required fields p1, v1, t1, v2, and t2—the initial pressure, initial volume, initial absolute temperature, final volume, and final absolute temperature. Every numeric field must be finite: missing required fields, empty strings, non-numeric text, NaN, and Infinity all fail immediately with invalid_input before any result is returned, and failed validation is not charged. Aliases are supported: initial_pressure and P1 for p1; initial_volume and V1 for v1; initial_temperature and T1 for t1; final_volume and V2 for v2; final_temperature and T2 for t2. Absolute temperatures t1 and t2 must be strictly positive kelvin: zero or negative kelvin is always rejected as invalid_input because the ideal-gas absolute scale does not admit non-positive temperatures in this model. Critically for this product contract, final volume zero is always rejected: the combined-gas rearrangement for final pressure divides by V2, so v2 equals zero is undefined and returns invalid_input with a message that names the zero final volume. After validation, the engine applies P2 equals P1 times V1 times T2 over V2 times T1 and rounds to a stable decimal precision so the same input always yields the same JSON across JavaScript engines. The same pure function powers the free in-browser tool and the API path.

Practical use, limits, pricing, and delivery channels

Each successful request is one billable item at $0.002; failed validation does not consume balance. Wire the endpoint into gas-law drills, contest answer checkers, process-sketch tools, or preprocessing steps where you already prefer explicit domain errors—such as rejecting zero final volume—over opaque black-box widgets that cannot explain why a bad input was refused.