Micromolar Calculators

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Micromolar (μM) is a concentration unit equal to one millionth of a mole per liter (10⁻⁶ mol/L). It is widely used in biochemistry and pharmacology to express the concentrations of enzymes, substrates, inhibitors, drugs, and cellular metabolites. Micromolar concentrations bridge the gap between millimolar (mM, physiological metabolite concentrations) and nanomolar (nM, hormone and drug concentrations). Key relationships: 1 μM = 1,000 nM = 0.001 mM = 10⁻⁶ M. Drug IC₅₀ values are commonly in the nM–μM range; enzyme Km values typically span μM–mM.

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Micromolar Conversion Table

  • 1 μM = 10⁻⁶ M
  • 1 μM = 1000 nM
  • 1 μM = 0.001 mM
  • 1 μM = 0.000001 M
  • 1 mM = 1000 μM
  • 1 nM = 0.001 μM

To convert μM to mg/mL: concentration (mg/mL) = μM × 10⁻³ × MW (g/mol). Or: μg/mL = μM × MW (Da) / 1000 × 1000 = μM × MW / 1000.

Example: 100 μM BSA (MW = 66,430 g/mol): mg/mL = 100 × 10⁻³ × 66,430 = 6.643 × 10³ mg/L = 6.643 mg/mL = 6643 μg/mL.

Typical Micromolar Values in Biology

  • Intracellular Ca²⁺ at rest: ~0.1 μM (100 nM)
  • ATP in cytoplasm: ~3000–5000 μM (3–5 mM)
  • Enzyme Km (typical): 10 μM – 10 mM
  • Drug IC₅₀ (moderate): 1–100 μM
  • Blood glucose: 4000–6000 μM (4–6 mM)
  • Plasma cholesterol: 3000–5200 μM (3–5.2 mM)

Preparing μM Solutions

From a 10 mM stock to 1 μM working solution: dilution factor = 10,000. Take 1 μL of stock into 9999 μL buffer, or use serial dilution: 10 mM → 100 μM (1:100 dilution) → 1 μM (1:100 dilution). Apply C₁V₁ = C₂V₂ for any dilution step.

Glossary

Micromolar (μM)
10⁻⁶ mol/L; concentration unit common in biochemistry and pharmacology; 1 μM = 1000 nM = 0.001 mM; μg/mL = μM × MW/1000; typical for enzyme Km and drug IC₅₀ values.
IC₅₀
The concentration of an inhibitor that reduces a biological activity by 50%; commonly in nM–μM range for drugs; lower IC₅₀ = more potent inhibitor.
Km (Michaelis Constant)
Substrate concentration at half-maximal enzyme velocity; typically 10 μM – 10 mM; low Km = high substrate affinity; high Km = low affinity; enzyme-and-substrate specific.

Frequently Asked Questions

Micromolar (μM) = 10⁻⁶ mol/L = one millionth of a molar. Conversion: 1 μM = 0.001 mM = 1000 nM = 10⁶ pM. To go from M to μM: multiply by 10⁶ (0.000025 M = 25 μM). To go from μM to M: divide by 10⁶. Context: intracellular signaling molecules and hormones are often in the pM–nM range; drug IC₅₀ and enzyme Km values span nM–μM; metabolites (glucose, ATP) are in the mM range. Knowing which unit applies to your molecule tells you immediately whether you're dealing with high-affinity or low-affinity interactions.

μg/mL = μM × MW / 1000, where MW is in g/mol (Da). Derivation: μM = μmol/L = nmol/mL; μg/mL = nmol/mL × MW (g/mol) × (1 μg/1000 ng) × 1000 ng/nmol = nmol/mL × MW/1000. Example: 50 μM IgG antibody (MW = 150,000 g/mol): μg/mL = 50 × 150,000/1000 = 7,500 μg/mL = 7.5 mg/mL. Reverse: μM = (μg/mL × 1000) / MW. Example: 1 mg/mL = 1000 μg/mL BSA (MW = 66,430): μM = 1000/66.430 = 15.1 μM.

Enzyme kinetics: Km (Michaelis constant) for most enzymes ranges from 0.01 μM (very tight substrate binding) to 10,000 μM (10 mM, weak binding). Most Km values fall in the 10–1000 μM range. Drug pharmacology: IC₅₀ (concentration that inhibits 50% of activity): < 0.001 μM = picomolar = highly potent drug; 0.001–1 μM = nanomolar (excellent potency); 1–10 μM = low micromolar (moderate potency); > 100 μM = weak (usually not drug-like). Most approved drugs have IC₅₀ values in the nM range for their primary target. Receptor binding: dissociation constants KD in nM range indicate high-affinity interactions.

Use C₁V₁ = C₂V₂. From 10 mM (10,000 μM) to 1 μM: dilution factor = 10,000. Take 1 μL of 10 mM stock and add to 9,999 μL buffer = 10,000 μL total → 1 μM. Or do serial dilution: 10 mM → 1:100 → 100 μM; then 100 μM → 1:100 → 1 μM. For each step: V₁ = C₂V₂/C₁. Example: need 1 mL of 1 μM from 10 mM stock: V₁ = (1 μM × 1 mL) / 10,000 μM = 0.0001 mL = 0.1 μL — a very small volume, prone to pipetting error. Better: two serial 1:100 dilutions to reach 1 μM.