Beer–Lambert concentration worksheet
Mistake: Entering a mass-based coefficient into the molar coefficient field.
Fix: Use a documented molar coefficient with exactly L/(mol·cm) units at the matching wavelength.
Calculators · Free
Beer–Lambert concentration worksheet
Calculate molar concentration from absorbance, known molar coefficient and optical path.
01Enter your values
Runs in your browserRuns offline in your browser. Once the page and required files have loaded, processing needs no internet.
02Beer–Lambert concentration worksheet
Runs in your browser
How it works
Calculate molar concentration from absorbance, known molar coefficient and optical path.
c = A / (εl); T% = 100 × 10⁻ᴬ
A known homogeneous single absorbing species, matched wavelength and matrix, and a validated linear measurement range are assumed. Scattering and stray light are not modeled. Enter a molar coefficient, not a mass or A1% coefficient. No chemical lookup, dilution recipe, dose or clinical interpretation. Works offline after loading.
Your data stays yours
Inputs are processed on this page and are never sent to a server.
About this tool
Use tool ↑Calculate molar concentration from absorbance, known molar coefficient and optical path.
Use c = A / (ε × l), with blank-corrected absorbance A, molar coefficient ε in L/(mol·cm), and path l in cm. Report concentration in mol/L, mmol/L and µmol/L. Transmittance is 100 × 10^(-A) percent. Convert only the path length when units change; coefficient units remain fixed.
How to use it
- Enter your values
Blank-corrected absorbance · Molar absorption coefficient · Optical path length
- Calculate / generate
Calculate molar concentration from absorbance, known molar coefficient and optical path.
- Result
Molar concentration: 0.00004 mol/L Millimolar concentration: 0.04 mmol/L Micromolar concentration: 40 µmol/L
Calculation method
- Use c = A / (ε × l), with blank-corrected absorbance A, molar coefficient ε in L/(mol·cm), and path l in cm.
- Report concentration in mol/L, mmol/L and µmol/L.
- Transmittance is 100 × 10^(-A) percent.
- Convert only the path length when units change; coefficient units remain fixed.
c = A / (εl); T% = 100 × 10⁻ᴬ
Beer–Lambert concentration worksheet
- Blank-corrected absorbance
- 0.6
- Molar absorption coefficient
- 15000 L/(mol·cm)
- Optical path length
- 1 cm
Result
Molar concentration: 0.00004 mol/L Millimolar concentration: 0.04 mmol/L Micromolar concentration: 40 µmol/L
Frequently asked questions
What does this result assume?
A known homogeneous single absorbing species, matched wavelength and matrix, and a validated linear measurement range are assumed. Scattering and stray light are not modeled. Enter a molar coefficient, not a mass or A1% coefficient. No chemical lookup, dilution recipe, dose or clinical interpretation. Works offline after loading.
Where does my data go?
Calculations run on your device. Form inputs are not sent to a server.
Terms and definitions
Enter your values
- Measurement system
The initial choice follows your browser region. Your choice is remembered on this device. Gallons are US gallons. Switching units keeps your numbers unchanged and interprets them in the new unit.
Numbers stay unchanged. Check the new unit and enter the intended measurement, or select an example for that system.
- Blank-corrected absorbance
Dimensionless absorbance at the coefficient’s wavelength; negative readings are rejected.
Enter a numerical value for this quantity.
Minimum: 0 · Maximum: 300
- Molar absorption coefficient
Known positive coefficient in L/(mol·cm), fixed in both length modes.
Enter a numerical value for this quantity. Use the unit shown beside this field. L/(mol·cm)
Minimum: 1e-12 · Maximum: 1000000000000 L/(mol·cm)
- Optical path length
Actual light path through the sample, not the vessel outside width.
Enter a numerical value for this quantity. Use the unit shown beside this field. cm / in
Minimum: 1e-12 · Maximum: 1000000000000 cm
Result
- Result
Use c = A / (ε × l), with blank-corrected absorbance A, molar coefficient ε in L/(mol·cm), and path l in cm. Report concentration in mol/L, mmol/L and µmol/L. Transmittance is 100 × 10^(-A) percent. Convert only the path length when units change; coefficient units remain fixed.
Calculated from your entries using the method below.
- Molar concentration
Concentration in mol/L under the supplied coefficient and path assumptions.
Calculated from your entries using the method below.
- Millimolar concentration
Molar concentration multiplied by 1000, in mmol/L.
Calculated from your entries using the method below.
- Micromolar concentration
Molar concentration multiplied by 1000000, in µmol/L.
Calculated from your entries using the method below.
- Value
Use c = A / (ε × l), with blank-corrected absorbance A, molar coefficient ε in L/(mol·cm), and path l in cm. Report concentration in mol/L, mmol/L and µmol/L. Transmittance is 100 × 10^(-A) percent. Convert only the path length when units change; coefficient units remain fixed.
Calculated from your entries using the method below.
- Unit
Convert only the path length when units change; coefficient units remain fixed.
Calculated from your entries using the method below.
- Transmittance
Calculated light transmission percentage corresponding to the entered absorbance.
Calculated from your entries using the method below.
Common mistakes and quick fixes
Limits and key assumptions
- A known homogeneous single absorbing species, matched wavelength and matrix, and a validated linear measurement range are assumed. Scattering and stray light are not modeled. Enter a molar coefficient, not a mass or A1% coefficient. No chemical lookup, dilution recipe, dose or clinical interpretation. Works offline after loading.
- Convert only the path length when units change; coefficient units remain fixed.
- Displayed results may be rounded; rounding does not add measurement precision.