Calculate lab solution concentrations and multi-solute recipes, or use the protein molarity calculator for kDa-based conversions. This free online tool also scales recipes for concentrated stocks.
For mass from a target percentage, choose Required mass from target concentration and select % w/v as the concentration unit.
Useful Checks
Use this with the Dilution Calculator when a prepared stock solution needs to be diluted or converted to a final working concentration.
Multi-solute mode calculates amounts for buffer, media, stain and assay recipes. Each component has its own concentration and unit.
Protein mode converts between protein mass concentration and molarity, or between protein mass and mole amount, using protein molecular weight in kDa.
Enter 1x working targets before choosing a stock multiplier. Results show both the 1x amount and the amount needed for the concentrated stock.
Components can use molar units, % w/v, % v/v, mg/mL, µg/mL, or g/L, with molecular weight requested only where it is needed.
Selected liquid acids can use editable % w/w assay and density values, so the result reports stock volume plus the pure-acid equivalent.
Minimum Inputs Needed
For single solute: choose a calculation mode, then enter the values that mode requests. Molecular weight or a selected compound is required only for molar conversions.
Required mass uses target concentration and final volume. Other directions use the displayed inputs, such as weighed mass, g/L or target molarity.
For % w/v mass: percent and final volume; molecular weight is not used.
For multi-solute: recipe volume and at least one component.
For protein mode: protein molecular weight in kDa and either concentration or amount.
Optional Settings
Calculator mode
Select Single solute for one compound, Multi-solute for a buffer or recipe, or Protein molarity for kDa-based protein conversions.
Calculation mode
Choose required mass, molarity from weighed mass and volume, final volume from weighed mass and target molarity, molarity from g/L, or g/L from molarity. For percentage-based mass calculations, choose Required mass from target concentration and select % w/v. Molecular weight is not needed for that mass calculation.
Stock multiplier
Use this only when preparing a concentrated stock such as 5x, 10x, or 20x. At 1x, the tool shows only the working-solution amount. Above 1x, it shows both the 1x working amount and the stock amount.
Compound search (optional)
Search by compound name, formula or abbreviation to fill molecular weight. Check the selected salt or hydrate form; you can also enter molecular weight manually.
Liquid acid stock
Appears for supported liquid acids. Edit the bottle assay in % w/w and density in g/mL before using the calculated stock volume.
Molecular weight
Needed for molar calculations if you do not select a compound.
Preferred output units
Choose a preferred mass, molarity or volume unit where shown. Auto picks a readable unit; display units do not change the calculated quantity.
Protein calculation mode
Choose mass concentration to molarity, molarity to mass concentration, protein mass to mole amount, or mole amount to protein mass.
Component unit
Choose each component's unit: molar, % w/v, % v/v, mg/mL, µg/mL or g/L. Use Add component for another row and Remove to discard a row.
How To Use: Single Solute
Select Single solute.
Select the calculation mode that names the result you need.
Enter the values requested for that direction, such as concentration, mass, molecular weight, or final volume.
Select a compound or enter molecular weight for molar calculations.
If liquid acid stock fields appear, check the % w/w assay and density against the bottle label or SDS.
Choose a stock multiplier only if making a concentrated stock.
Click Calculate.
How To Use: Multi-Solute Recipe
Select Multi-solute.
Enter the final recipe volume.
Choose 1x, 5x, 10x, or a custom stock multiplier.
Add each component and enter its 1x target.
Choose the unit for each component: molar, % w/v, % v/v, mg/mL, µg/mL, or g/L.
Enter molecular weight only for components using molar units, unless you select a compound from search.
For selected liquid acids, check the % w/w assay and density shown inside that component row.
Click Calculate.
How To Use: Protein Molarity
Select Protein molarity.
Enter the protein molecular weight in kDa.
Choose one of the four conversion directions: concentration-to-concentration or amount-to-amount.
Enter the concentration or amount and choose the input/output units.
Click Calculate.
Understanding The Results
The result shows the requested quantity: mass, molarity, final volume, g/L, protein concentration, protein mass or mole amount.
For liquid acids, the result reports stock volume to add and the pure-acid equivalent.
At 1x, the result shows only the amount for the final working solution.
Above 1x, results show both the working-solution amount and the selected stock amount. On narrow screens, read the complete amounts in the detailed result.
In multi-solute stock mode, each row keeps the 1x target beside the stock target and amount to add.
The final step tells you to bring the complete mixture to the final recipe volume, not to add that much water on top.
Warnings may appear for very small masses, high concentrations, high % v/v totals, or solubility concerns.
Protein mode shows the converted value, direction, output unit and molecular weight. Concentration conversions do not require a sample volume; mass-to-mole conversions use total amount.
Click Calculate once to show a result. Later numeric changes update it automatically. Check the active mode, calculation direction and units whenever you change inputs.
Accepted Input Formats
Molar units: M, mM, µM, nM.
Mass concentration units: % w/v, mg/mL, µg/mL and g/L. The % v/v option is available for multi-solute component volumes.
Volume units: L, mL, µL.
Protein mode accepts kDa for molecular weight, common mass concentration units, molar concentration units, mass amount units, and mole amount units.
Assumptions And Limitations
Compound values are reference values from a curated offline list. Verify the exact reagent form you use.
Liquid acid defaults are starter values for common concentrated acids; supplier assay, density, temperature, and dilution can vary.
Solubility warnings are approximate.
% w/v means grams per 100 mL final solution.
% v/v is a volume-to-add calculation, not a mass calculation.
For multi-solute stock recipes, component targets are treated as 1x working targets and multiplied for the stock recipe.
Use the molecular weight of the protein species being counted. Monomer molecular weight gives monomer-equivalent molarity; an intact dimer requires the dimer's molecular weight. Tags, cleavage and glycosylation can also change this value.
Protein molarity is an amount-concentration conversion; it does not predict activity, oligomerization state, purity, or functional protein concentration.
Examples
Single solute: To make 100 mL of 10 mM Tris, search Tris or enter the molecular weight, set 10 mM and 100 mL, then calculate the mass.
Liquid acid: To make 100 mL of 100 mM HCl, select hydrochloric acid, check the 37% w/w assay and 1.19 g/mL density, then use the calculated concentrated-acid volume.
Multi-solute: To make a 5x buffer stock, enter the final stock volume, choose 5x, add each component at its 1x target, then prepare the listed 5x amounts and bring the mixture to the final volume.
Protein: For a 50 kDa protein at 1 mg/mL, choose mass concentration to molarity. The result is 20 µM.
Protein mass to pmol: Select Protein molarity, choose protein mass to mole amount, and enter 50 kDa and 25 µg. Choose pmol output. The result is 500 pmol: 25 × 1000 / 50. This converts a total mass, not a concentration, so no sample volume is required.
Monomer or dimer: At 1 mg/mL, a protein with 50 kDa subunits has 20 µM monomer equivalents. If all subunits form intact 100 kDa dimers, enter 100 kDa to obtain 10 µM dimers. For a mixture of monomers and dimers, total mass concentration alone cannot determine each species' concentration.
Use this result with other tools
Receiving a recipe:Buffer Calculator has a Send components to Molarity Calculator button. It fills the multi-component recipe with component names, targets and units, available molecular weights/formulae and final volume. Dry solids keep their molar targets and selected forms. Liquid reagents and component stocks arrive as % v/v of the reagent being added; the component name records the selected bottle assay and density or stock molarity.
Review the imported quantities before editing or adding rows. Changing final volume scales the amounts, and a stock multiplier scales the imported targets. A reagent-volume percentage is not the solute's molarity, so changing to a molar unit requires the corresponding solute concentration. Buffer pH and acid/base balance are not recalculated here; return to Buffer Calculator if the design or bottle/stock assumptions change.
On a narrow screen, scroll within the component list or result table to see every column. Keyboard users can Tab to either labelled region and use the arrow keys to scroll.
Manual follow-up: use the calculated stock concentration in Dilution Calculator to plan a dilution. Transfer the numeric concentration and its unit yourself; Molarity Calculator has no direct outbound send button. Keep mass concentration, molar concentration and percentage modes distinct when moving values.
Use note: These tools are for research and educational planning. Check important calculations and sequence designs before ordering reagents or running experiments.