Mole Calculator
The general mole hub: solve for whichever of mass, molar mass, moles, volume, or particle count you don't have.
🔢 What is the Mole Calculator?
The Mole Calculator is a general-purpose hub tool covering every common mole-related conversion in introductory chemistry. Rather than being locked into one fixed direction, it lets you choose which quantity you already know and which one you want solved, across two families of relationships: mass, molar mass, and moles (n = mass ÷ M), and moles, gas volume at standard temperature and pressure, and particle count (V = n × 22.4 L/mol, N = n × NA).
This tool is meant for anyone who does not need just one fixed conversion, students working through a mixed problem set where sometimes mass is unknown and sometimes molar mass is unknown, lab technicians back-calculating a molar mass from a measured mass and mole count, or anyone connecting gas volume, particle count, and moles together in one place.
It is important to distinguish this hub tool from the site's more focused mole calculators. If you specifically and only need to convert a known mass in grams to moles, the Grams to Moles Calculator is faster and more direct for that one search. If you want a deeper explanation of Avogadro's constant itself, its exact CODATA value, and its historical definition, the Avogadro's Number Calculator covers that in more depth. This calculator sits above both as the general "solve for whatever I don't have" tool.
Mode 1 (Mass ↔ Moles) uses a Solve For selector to pick which of mass, molar mass, or moles is unknown, then computes it from the other two using n = mass ÷ M rearranged as needed. Mode 2 (Moles ↔ Volume/Particles) works the same way for the STP molar volume and Avogadro's number relationships, and conveniently accepts either a known volume or a known particle count when solving for moles.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — Solve for moles (CO2 sample)
How many moles are in 44 g of CO2 (M = 44.01 g/mol)?
Example 2 — Solve for mass (oxygen gas)
What is the mass of 0.5 mol of O2 (M = 32 g/mol)?
Example 3 — Solve for molar mass
An 8 g sample contains exactly 0.25 mol. What is its molar mass?
Example 4 — Solve for moles from gas volume at STP
How many moles is 11.2 L of gas at STP?
Example 5 — Solve for gas volume from moles
What volume does 2 mol of gas occupy at STP?
❓ Frequently Asked Questions
🔗 Related Calculators
What does a mole calculator do?
A mole calculator solves for one unknown quantity in a set of related mole formulas, given the other known quantities. This calculator covers two families of relationships: mass, molar mass, and moles (n = mass / M), and moles, volume at STP, and particle count (V = n x 22.4, N = n x NA).
How do I solve for mass, molar mass, or moles?
In Mass to Moles mode, use the Solve For dropdown to choose which quantity is unknown, then enter the other two. Solving for moles uses n = mass / M, solving for mass uses mass = n x M, and solving for molar mass uses M = mass / n.
How do I solve for moles, volume, or particle count at STP?
In Moles to Volume/Particles mode, choose which quantity is unknown from the Solve For dropdown. Solving for moles accepts either a volume at STP (n = V / 22.4) or a particle count (n = N / NA). Solving for volume uses V = n x 22.4, and solving for particle count uses N = n x NA.
What is the molar volume at STP?
At standard temperature and pressure (STP, defined here as 0 degrees Celsius and 1 atmosphere), one mole of any ideal gas occupies 22.4 liters. This is why 22.4 L/mol is used to convert directly between moles of gas and volume without needing to know the gas's identity or molar mass.
What is the difference between this calculator and the Grams to Moles Calculator?
The Grams to Moles Calculator does one specific conversion, grams to moles, as quickly and simply as possible. This Mole Calculator is a broader hub: it can solve for mass, molar mass, or moles in that same family (choosing which is unknown), and it also covers a second family of relationships connecting moles to gas volume at STP and to particle count. Use this page when you need more flexibility than a single fixed direction.
What is the difference between this calculator and the Avogadro's Number Calculator?
The Avogadro's Number Calculator focuses specifically on the moles-to-particles relationship (N = n x NA) with detailed explanatory content about the constant itself, its history, and its exact CODATA value. This Mole Calculator includes that same relationship as one option inside its second mode, but frames it as one of several interchangeable mole conversions inside a general-purpose hub tool, alongside mass and volume.
Can I solve for molar mass if I know both mass and moles?
Yes. Select Molar Mass in the Solve For dropdown of Mass to Moles mode, then enter the mass and the number of moles. The calculator computes M = mass / n. This is useful when you have experimental mass and mole data and need to identify or verify an unknown substance's molar mass.
Does the Moles to Volume/Particles mode only work for gases?
The 22.4 L/mol molar volume relationship (V = n x 22.4) is specific to gases at STP, since only gases have a volume that depends purely on the number of moles present, independent of what the substance actually is. The moles-to-particles relationship (N = n x NA), however, applies to any substance in any phase, solid, liquid, or gas.
Why does solving for moles in Mode 2 accept either volume or particles?
Moles is the pivot value that connects to both volume and particle count independently, so either one alone is enough to determine moles. If you know the gas volume at STP, the calculator uses n = V / 22.4. If instead you know the particle count, it uses n = N / NA. You only need to fill in whichever one you actually have.
Is STP the same as NTP or STAP?
No, and different sources use slightly different definitions of standard conditions, which is a common source of confusion. This calculator uses the traditional STP definition of 0 degrees Celsius and 1 atmosphere, giving 22.4 L/mol, which remains the most common convention in general chemistry courses. IUPAC's more recent STP definition (0 degrees Celsius, 100 kPa) gives a slightly different molar volume of 22.7 L/mol, and NTP (Normal Temperature and Pressure) uses yet another convention entirely.