All calculatorsMolarity Calculator
Compute solution molarity M (mol·L⁻¹) from moles n and volume V, or derive n from mass m and molar mass M. See steps, and visualize results with a mini bar chart and a molarity gauge.
Background
By definition, M = n / V with volume in liters. If you don’t have moles, first compute n = m / M using the solute mass m (g) and molar mass M (g·mol⁻¹).
How to use this calculator
- If you know moles: enter n and V → M = n / V.
- If you know mass: enter m and molar mass M, plus V → n = m / M → M = n / V.
- Units: volume is converted to liters; molarity is mol·L⁻¹.
Formula & Equation Used
Molarity: M = n / V
Moles from mass: n = m / M
Example Problems & Step-by-Step Solutions
Example 1 — 5.00 g NaCl in 250 mL
M(NaCl) ≈ 58.44 g·mol⁻¹ → n = 5.00 / 58.44 = 0.0856 mol; V = 0.250 L → M = 0.342 mol·L⁻¹.
Example 2 — 0.100 mol in 100 mL
V = 0.100 L → M = 0.100 / 0.100 = 1.00 mol·L⁻¹.
Example 3 — 18.015 g H₂O in 500 mL
M(H₂O) = 18.015 g·mol⁻¹ → n = 18.015 / 18.015 = 1.000 mol; V = 0.500 L → M = 2.00 mol·L⁻¹.
Frequently Asked Questions
Q: Can I enter volume in mL?
Yes. We convert mL to L automatically.
Q: Do I need moles?
No. You can give mass and molar mass to compute moles first.
Q: What does “Round to sensible significant figures” do?
It reports values to ~3 significant figures (switching to scientific notation for very small/large numbers).
