Gas Laws Calculator

Calculate gas law problems with clear explanations. Perfect for chemistry students and professionals.

Gas Laws Calculator

Choose the gas law that applies to your problem

Initial Conditions

Final Conditions

Calculation Results

Ready to Calculate?

Select a gas law above and enter your known values to get started.

What is Gas Laws Calculator

Gas law problems can be confusing because they involve several variables that change at the same time. Pressure, volume, temperature, and the amount of gas all affect each other, and keeping track of them can be difficult.

This Gas Laws Calculator is designed to make those relationships easier to understand. You start by choosing the gas law you want to use. The calculator then shows only the values you need to enter, so there's no guesswork involved.

Once you enter the known values, the calculator finds the missing one instantly. It also converts units automatically, so you don't need to worry about switching between Celsius and Kelvin or converting pressure units.

What makes this calculator especially useful is the clear explanation that follows each result. You can see which gas law was applied, how the formula was used, and how the final value was calculated. This helps you understand the process instead of just memorizing equations.

The clean layout keeps everything focused on one problem at a time. There are no unnecessary buttons or distractions, which makes the calculator easy to use on both desktop and mobile devices.

Understanding the Gas Laws

Boyle's Law

Pressure and volume are inversely related when temperature is constant. If pressure increases, volume decreases.

P₁ × V₁ = P₂ × V₂

Charles's Law

Volume and temperature are directly related when pressure is constant. Gas expands when heated.

V₁ / T₁ = V₂ / T₂

Gay-Lussac's Law

Pressure and temperature are directly related when volume is constant. Pressure increases with temperature.

P₁ / T₁ = P₂ / T₂

Combined Gas Law

Combines Boyle's, Charles's, and Gay-Lussac's laws. Use when two or more variables change.

P₁V₁ / T₁ = P₂V₂ / T₂

Ideal Gas Law

Relates pressure, volume, temperature, and amount of gas. Most comprehensive gas law.

PV = nRT

When to Use Each Gas Law

Boyle's Law - Pressure Changes

Use when pressure changes but temperature stays constant. Common in scuba diving, syringes, and piston engines.

Example: What volume will 2.0 L of gas occupy at 3.0 atm if it was originally at 1.0 atm?

Charles's Law - Temperature Changes

Use when temperature changes but pressure stays constant. Important for hot air balloons and understanding thermal expansion.

Example: If a gas occupies 500 mL at 20°C, what volume will it occupy at 50°C?

Gay-Lussac's Law - Sealed Containers

Use when volume is constant but temperature or pressure changes. Applies to pressure cookers and spray cans.

Example: If pressure is 2.0 atm at 25°C in a sealed container, what pressure will it be at 100°C?

Combined Gas Law - Multiple Changes

Use when two or three variables (P, V, T) change simultaneously. Most realistic for real-world gas problems.

Example: A gas at 2 atm and 300 K occupies 10 L. What volume will it occupy at 3 atm and 400 K?

Ideal Gas Law - Complete Information

Use when you know the amount of gas (moles) and need to find any missing variable. Most powerful but requires more information.

Example: How many moles of gas are in a 5.0 L container at 2 atm and 300 K?

Tips for Gas Law Problems

Always Convert Temperatures to Kelvin

Gas laws require absolute temperature (Kelvin). Convert Celsius to Kelvin by adding 273.15.

Identify What's Constant

Determine which variables stay the same. This tells you which gas law to use.

Check Units Carefully

Make sure all pressure, volume, and temperature units are consistent before calculating.

Use the Right Gas Constant

For the Ideal Gas Law, R = 0.0821 L·atm·mol⁻¹·K⁻¹ when using atm, L, and moles.

Common Mistakes to Avoid

Don't forget that temperature must be in Kelvin for all gas laws except simple unit conversions. Also remember that Boyle's Law only applies when temperature is constant.

Gas Laws Questions Students Ask

Why do gas laws require Kelvin temperature?

Gas laws are based on absolute temperature scales. At absolute zero (0 K = -273°C), molecular motion theoretically stops. Celsius and Fahrenheit are relative scales that can be negative, which would give impossible results in gas calculations.

When should I use the Combined Gas Law vs individual laws?

Use individual laws when only one variable changes (like just pressure or just temperature). Use the Combined Gas Law when multiple variables change simultaneously, which is more realistic for actual gas behavior.

What's the difference between ideal gases and real gases?

Ideal gases follow gas laws perfectly - molecules have no volume and don't interact. Real gases deviate from ideal behavior at high pressures or low temperatures. The Ideal Gas Law works best for dilute gases at normal conditions.

How do I know which R value to use?

Choose R based on your units: 0.0821 L·atm·mol⁻¹·K⁻¹ (atm, L, moles), 8.314 J·mol⁻¹·K⁻¹ (Pa, m³, moles), or 62.4 L·mmHg·mol⁻¹·K⁻¹ (mmHg, L, moles). The calculator handles this automatically.