Resuspension Calculator
Calculate how much solvent (water, buffer, media, etc.) to add to reach your target concentration.
What this resuspension calculator does
A resuspension calculation answers one practical question: how much liquid should I add to a known amount of dry material? This tool supports both mass-based concentrations (like mg/mL) and molar concentrations (like mM), so it works for many lab workflows: peptides, primers, enzymes, salts, small molecules, and more.
Core equation
The underlying relationship is simple:
Volume = Amount / Target Concentration
- If your concentration is mass-based, use mass (g, mg, µg) in the numerator.
- If your concentration is molar, use moles (mol, mmol, µmol) in the numerator.
- When you need to switch between mass and moles, use molecular weight:
moles = mass (g) / molecular weight (g/mol)
How to use it
- Enter the amount of dry solute you have.
- Select the amount unit (mass or moles).
- Optionally enter molecular weight (required only for mass↔molar conversion cases).
- Enter your target concentration value and unit.
- Click Calculate Volume to get the solvent volume in liters, milliliters, and microliters.
Worked examples
Example 1: Mass concentration
You have 50 mg of compound and want 10 mg/mL. Required volume = 50 / 10 = 5 mL.
Example 2: Molar concentration from moles
You have 2 µmol and want 100 µM. Convert: 2 µmol = 2×10-6 mol, 100 µM = 1×10-4 mol/L. Volume = (2×10-6) / (1×10-4) = 0.02 L = 20 mL.
Example 3: Molar concentration from mass (MW needed)
You have 25 mg of a compound with MW = 500 g/mol, and want 5 mM. Mass in grams = 0.025 g; moles = 0.025 / 500 = 0.00005 mol. 5 mM = 0.005 mol/L. Volume = 0.00005 / 0.005 = 0.01 L = 10 mL.
Quick unit reference
| Unit | Equivalent base unit |
|---|---|
| 1 mg/mL | 1 g/L |
| 1 µg/mL | 0.001 g/L |
| 1 mM | 0.001 mol/L |
| 1 µM | 1×10-6 mol/L |
Common mistakes to avoid
- Mixing up mg/mL and µg/mL (1000x difference).
- Forgetting molecular weight when converting between mass and molarity.
- Using final volume incorrectly (especially after adding stabilizers or salts).
- Not accounting for purity or hydrate forms when precision matters.
Practical lab tips
Start with partial volume
Add ~70–90% of the calculated solvent first, dissolve completely, then bring up to final volume. This improves accuracy for stubborn compounds.
Record conditions
Note solvent type, pH, temperature, and lot number in your notebook or ELN. These details can strongly affect solubility and reproducibility.
Aliquot and store smartly
If material is freeze-thaw sensitive, aliquot into single-use tubes and store at the recommended temperature.