Advanced Conversion Form
Enter molecular weight for the exact substance. Use salt factor for hydrate or salt corrections.
Formula Used
The core conversion uses molecular weight in grams per mole.
ug/mL = uM × molecular weight ÷ 1000
With options, the calculator uses this wider expression.
ug/mL = (uM × MW × salt factor × dilution factor) ÷ (1000 × purity fraction)
Reverse mode uses this expression.
uM = (ug/mL × 1000 × purity fraction) ÷ (MW × salt factor × dilution factor)
How to Use This Calculator
Example Data Table
| Compound Type | uM | MW | Result |
|---|---|---|---|
| Small molecule | 10 | 500 g/mol | 5 ug/mL |
| Peptide | 2 | 1500 g/mol | 3 ug/mL |
| Dye stock | 25 | 750 g/mol | 18.75 ug/mL |
| Reference standard | 1 | 300 g/mol | 0.3 ug/mL |
Reliable Concentration Planning
Why This Conversion Matters
Micromolar values describe molar concentration. Micrograms per milliliter describe mass concentration. Labs often need both units. A protocol may list a working dose in uM. A balance, vial, or certificate may require ug/mL. This calculator joins those two views. It uses molecular weight as the bridge.
Molecular Weight Drives Accuracy
Each compound has its own molecular weight. That value changes the mass needed for one micromolar. A heavy molecule needs more mass. A light molecule needs less mass. Always use the exact molecular weight for the material you will weigh. Check whether the label lists free base, salt, hydrate, or mixture details.
Purity and Salt Factors
Purity matters when the weighed material is not fully active compound. A 95 percent material needs a small mass increase. The purity option applies that correction. The salt factor helps when a supplier gives a free base target but the bottle contains a salt form. Use one when no correction is needed.
Dilution Planning
Dilution factor supports stock preparation. A final 10 uM solution may come from a 100x stock. In that case, the stock must be stronger than the final solution. Enter the dilution factor to calculate the stock mass concentration. Keep the factor at one for direct working solutions.
Mass for a Target Volume
The form also estimates total material mass. It multiplies the calculated ug/mL value by target volume. Then it converts micrograms to milligrams. This helps when preparing assay plates, calibration standards, or screening stocks. Small volumes can be entered in uL. Larger batches can be entered in liters.
Before Weighing
Review the certificate before making any stock. Confirm the lot number, water content, and assay basis. Some suppliers report purity by area. Others report purity by weight. Those details can affect mass planning. Use the correction that matches your validated method. If your protocol is regulated, follow approved laboratory documents.
Handling Small Values
Very low concentrations can produce tiny mass values. Weighing those masses may be impractical. Prepare a stronger stock first. Then dilute it with clean solvent. This reduces weighing error. It also improves repeatability between runs. Use calibrated pipettes for small volume transfers. Label each intermediate stock clearly.
Checking the Result
Compare the calculated value with past preparations. Large differences usually mean a wrong unit, wrong molecular weight, or missed dilution. Check whether the intended unit was uM, mM, ng/mL, or mg/mL. A simple review can prevent failed assays. Repeat the review before sharing calculated stock sheets with teammates. Check entries before sharing stock sheets with teammates.
Good Lab Practice
Record the molecular weight source. Record the compound form. Record purity and dilution factor. These notes make repeated preparation easier. They also help reviewers trace concentration choices. Use sensible significant figures. Do not report more precision than the input data supports. Clear records make future dilution checks safer and faster.
Frequently Asked Questions
1. What does uM mean?
uM means micromolar. It is one micromole of solute per liter of solution. It describes the number of molecules, not their mass.
2. What does ug/mL mean?
ug/mL means micrograms per milliliter. It describes mass concentration. It depends on how much compound mass exists in each milliliter.
3. Why is molecular weight required?
Molecular weight connects moles to grams. Without it, a molar concentration cannot become a mass concentration.
4. What is the basic uM to ug/mL formula?
The basic formula is ug/mL equals uM multiplied by molecular weight, then divided by 1000.
5. When should I use purity correction?
Use purity correction when the material is less than 100 percent active compound. The calculator increases the required weighed concentration.
6. What is salt factor?
Salt factor adjusts molecular weight for salt or hydrate forms. Use one when the listed molecular weight already matches your bottle.
7. What does dilution factor do?
Dilution factor scales the calculated stock concentration. A 100x stock uses a dilution factor of 100.
8. Can I convert ug/mL back to uM?
Yes. Choose the reverse mode. Enter ug/mL, molecular weight, purity, dilution factor, and salt factor.
9. Does volume affect ug/mL?
Volume does not change concentration by itself. It changes total material mass required for preparing that concentration.
10. Can this handle peptides?
Yes. Use the peptide molecular weight. Add salt or hydrate correction only when your material form requires it.
11. How should I document results?
Save the result with compound name, molecular weight, purity, salt factor, and dilution factor. Record molecular weight sources to keep future work consistent.