Find the mass to weigh for a target molar concentration, solve C1V1 = C2V2 dilutions, and convert between M, mM, µM, nM, pM and mg/mL. It all runs in your browser; nothing you enter is sent anywhere.
Results are rounded to 4 significant figures. Check the MW on your reagent’s label before weighing.
Molarity is moles of solute per liter of solution. Multiply the concentration you want by the final volume to get moles, then by the molecular weight to get grams. Rearranged, C = m ÷ (V × MW) and V = m ÷ (C × MW).
The amount of solute you take from the stock is the amount that ends up in the diluted solution. Solve for the missing term, for example V1 = C2 × V2 ÷ C1. The diluent to add is V2 − V1, and the dilution factor is C1 ÷ C2.
Molar units step by factors of 1,000. Because 1 mg/mL equals 1 g/L, multiplying molarity (mol/L) by MW (g/mol) gives mass concentration in mg/mL directly; divide by MW to go back.
| Unit | Name | In mol/L | 1 M equals |
|---|---|---|---|
| M | molar | 1 | 1 M |
| mM | millimolar | 10⁻³ (0.001) | 1,000 mM |
| µM | micromolar | 10⁻⁶ | 10⁶ µM |
| nM | nanomolar | 10⁻⁹ | 10⁹ nM |
| pM | picomolar | 10⁻¹² | 10¹² pM |
Dissolve 60.57 g of Tris base in about 400 mL of water, adjust the pH with HCl, then adjust the volume to 500 mL with water. Adjust the volume last, because adding acid changes it.
Add 1 µL of the 10 mM dNTP mix, then the other reaction components, and water to a final volume of 50 µL. 200 µM of each dNTP is a common final concentration; follow your polymerase’s protocol if it says otherwise.
Molarity (M) is moles of solute per liter of solution (mol/L). Molality (m) is moles of solute per kilogram of solvent (mol/kg). Molarity is what you use when you prepare a solution to a final volume at the bench. Because liquid volume changes slightly with temperature, molarity does too, while molality does not. This calculator works in molarity.
Each step on the scale M → mM → µM → nM → pM is a factor of 1,000. To go to a larger unit, divide by 1,000; to go to a smaller unit, multiply by 1,000. For example, 250 mM = 0.25 M, and 50 µM = 0.05 mM = 50,000 nM. The unit converter tab above shows every unit at once.
1 mg/mL is the same as 1 g/L, so divide by the molecular weight in g/mol: M = (mg/mL) ÷ MW. A 2 mg/mL solution of a 50 kDa protein (50,000 g/mol) is 2 ÷ 50,000 = 4 × 10⁻⁵ M, or 40 µM. Going the other way, multiply molarity by MW to get g/L (mg/mL).
Use the formula weight on the label of the exact form you are weighing, including any water of crystallization. MgCl₂ · 6H₂O is 203.30 g/mol, while anhydrous MgCl₂ is 95.21 g/mol, so using the wrong one makes your solution about twice as strong or half as strong as intended. The values in the reagent list are for the forms named there.
Yes. The equation works with any concentration unit, as long as C1 and C2 are in the same kind of unit (both molar, both mass per volume, or both “×”). The calculator converts between M, mM, µM and the other units for you. For very large dilutions, such as 10,000-fold, dilute in two or more steps (for example 100-fold, then 100-fold). Pipetting error is largest at very small volumes, and a stepwise dilution keeps every transfer at a volume you can pipette accurately.
dATP, dCTP, dGTP and dTTP at 10 mM each, the stock used in Example 2.
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A single 100 mM nucleotide solution. A 10-fold dilution gives a 10 mM working solution.
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Supplied as a 10× concentrate. Dilute 10-fold with deionized water (1 part + 9 parts) for a 1× working solution.
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