Molarity Calculator

Tap what you want to calculate.

m=M×MW×V

Mass (m)

Molarity (M)

Molar mass (MW)

Volume (V)

Result

90.08 mg

Formula: mass = molarity × volume × molecular weight

Save molarity calculations across devices

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Step 1

Pick an equation

Step 2

Tap what to solve for

Step 3

Enter values & units

Step 4

Copy or save (sign in)

Online molarity calculator

Use the website when you need the grams for a molar solution, a molarity from moles and volume, or a mass concentration — without installing an app or creating an account. Sign in to keep saved calculations synced with the BiyoLabs mobile app.

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BiyoLabs molarity calculator solving mass from molarity, volume, and molecular weight

About this molarity calculator

This free online molarity calculator covers the three formulas you actually use at the bench: m = M × V × MW to weigh out a solid for a target molarity, M = n / V for molar concentration from moles and volume, and c = m / V for mass concentration. Tap any variable in the formula bar to make it the unknown, pick a compound from the built-in molecular weight list, and switch between M, mM, µM, nM, g, mg, µg, L, mL, and µL as needed.

How it works

1Choose mass prep, molarity, or mass concentration.
2Tap the variable you want to solve for in the formula.
3Copy the result, or sign in to sync saved calculations.

Who is this for?

Chemistry and biology students, researchers, and lab teams who prepare stock solutions, standards, and buffers — anyone who needs a molarity, a weigh-out, or a unit conversion without reaching for a spreadsheet.

Molarity calculator FAQ

Is the BiyoLabs molarity calculator free?

Yes. The public molarity calculator is free and needs no login. Pick an equation, tap the variable you want to solve for, enter the rest, and read the result — grams to weigh out, molarity, moles, volume, or mass concentration.

How do I calculate the grams needed for a molar solution?

Use the mass prep equation: m = M × V × MW. Enter the molarity you want (for example 50 mM), the final volume, and the molecular weight of the compound. The calculator returns the mass to weigh out in g or mg. Any variable in the formula can be the unknown — tap it in the formula bar.

What is the molarity formula?

Molarity (M) is moles of solute per litre of solution: M = n / V. The molarity equation in this tool solves for M, n, or V, so you can also work out how many moles are in a volume of a known concentration, or what volume a given number of moles makes.

Can I convert mg/mL to mM?

Yes. Use the mass prep or mass-concentration equation with the molecular weight: mass concentration (c = m / V) links g/L, mg/mL, and µg/mL to molar units, so you can go from a mg/mL stock to mM and back.

Do I have to look up molecular weights myself?

No. The molecular weight field has a built-in chemical list — pick a compound and its MW is filled in. You can also add your own custom MW presets and pin the ones you use most; they are shared with the medium/buffer tool.

Which units does the molarity calculator support?

Molar units (M, mM, µM, nM), mass units (kg, g, mg, µg), volumes (L, mL, µL), mass/volume concentrations (g/L, mg/mL, µg/mL), and g/mol for molecular weight. You can also set how many decimal places the result shows.

Does this page save my calculations?

No. This public page is for quick calculations only — nothing is saved to an account. For saved calculations that sync with the BiyoLabs mobile app, sign in and use /app/molarity.