Elysia Tools

Browse tools, examples, visual explainers, and topic guides from one clear workspace.

Top Categories

Hubs

Language
ZHESPTRUFRDEEN

Elysia Tools

Navigation

Education

Molar Extinction Coefficient & Beer-Lambert (A = ε·c·l)

· Last updated：2026-08-22

Solve A, ε, c or l from the Beer-Lambert law A = ε·c·l, with M/mM/µM/nM and cm/mm unit support.

Execution

Run this tool

Fill in the form, run the tool, and review the result in one place.

Samples

Examples that match this tool

Related

Continue with connected tools and hubs

Written by the Elysia Tools team

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category
Education
Input types
select, number
Output type
json
Sample coverage
4
API ready
Yes

Overview

The Molar Extinction Coefficient & Beer-Lambert Calculator solves for any variable in the Beer-Lambert equation (A = ε·c·l)—absorbance, molar extinction coefficient, concentration, or optical path length—with built-in unit conversion for M, mM, µM, nM, cm, and mm.

When to use

  • Determining unknown solute concentrations from spectrophotometric absorbance readings.
  • Calculating molar absorptivity (ε) for novel chromophores, proteins, or chemical dyes from standard solutions.
  • Predicting expected absorbance values or selecting optimal cuvette path lengths for kinetic assays.

How it works

  1. 1Select the variable you want to compute (Absorbance, Extinction Coefficient, Concentration, or Path Length).
  2. 2Enter the known values and specify the appropriate concentration (M, mM, µM, nM) and path length (cm, mm) units.
  3. 3Adjust the output decimal precision to generate the final calculated value and underlying formula substitution.

Use cases

  • Enzymatic activity assays monitoring NADH or NADPH consumption and production at 340 nm.
  • Nucleic acid and protein concentration determination via UV absorbance at 260 nm and 280 nm.
  • Analytical chemistry workflows establishing calibration baselines and characterizing newly synthesized dyes.

Examples

1. Verifying NADH Absorbance in an Enzyme Assay

Biochemist

Background

A researcher is running a dehydrogenase enzyme coupled assay producing 100 µM NADH in a standard 1 cm cuvette.

Problem

Calculate the expected absorbance at 340 nm to confirm whether the assay will fall within the linear range of the spectrophotometer.

How to use

Set Solve For to 'Absorbance (A)', enter Extinction Coefficient as 6220, Concentration as 100 with unit 'uM', and Path Length as 1 with unit 'cm'.

Outcome

Returns an expected absorbance of A = 0.6220.

2. Determining Molar Absorptivity of a Synthetic Fluorophore

Organic Chemist

Background

A chemist synthesizes a dye and prepares a 50 µM standard solution that produces an absorbance of 1.200 in a 1 cm cuvette.

Problem

Determine the molar extinction coefficient (ε) to report in a publication.

How to use

Set Solve For to 'Extinction Coefficient ε (M⁻¹cm⁻¹)', enter Absorbance as 1.2, Concentration as 50 with unit 'uM', and Path Length as 1 with unit 'cm'.

Outcome

FAQ

What is the Beer-Lambert law equation?

The Beer-Lambert law is A = ε·c·l, where A is absorbance (dimensionless), ε is the molar extinction coefficient (M⁻¹cm⁻¹), c is molar concentration (mol/L), and l is the optical path length (cm).

How does the tool handle concentration and path length unit conversions?

Non-standard units such as mM, µM, nM, and mm are automatically converted to M (mol/L) and cm before performing calculations to match the standard dimension of ε (M⁻¹cm⁻¹).

What is the standard extinction coefficient for NADH at 340 nm?

The accepted molar extinction coefficient for NADH at 340 nm is 6,220 M⁻¹cm⁻¹ (6.22 × 10³ M⁻¹cm⁻¹).

Why does absorbance have no units?

Absorbance is defined as the logarithm of the ratio of incident light intensity to transmitted light intensity (log₁₀(I₀/I)), making it a dimensionless value.

Can I solve for concentration when using a microplate reader with a non-standard path length?

Yes, you can enter custom path lengths directly in millimeters or centimeters to accurately determine sample concentrations.

Hub

Absorbance Quantification and Acid-Base Calculations

Turn instrument readings into concentrations you can defend — convert between absorbance and transmittance, solve the Beer-Lambert law for whichever variable is missing, walk the nucleic acid chain from A260 to micrograms to nanomolar to copies per microliter, predict pH from strong acid and base concentrations, design buffers with Henderson-Hasselbalch, and check dissociation through molar conductivity.

Home
Tools3201
Samples593
Visualizations465
Viewers103
Hubs233
Tags333
Images, Audio & Video657

Image, audio, and video processing, conversion, and optimization tools

Math, Date & Finance644

Calculators, numerics, date logic, statistics, and finance tools

Design & Color297

Color, layout, graphics, visual styling, and design helper tools

Text & Writing209

Writing, cleanup, formatting, extraction, and text analysis tools

Developer & Web193

Developer utilities, networking, web debugging, and automation helpers

Conversion & Encoding175

Format, file, archive, unit, and encoding conversion tools

FLAC/WAV Source Screening and Evidence Handoff
Self-Hosted Giveaway Widget Review and Embed Handoff
Stripe Promo Code Batch Review and Import Preflight
Batch Photo Culling Review and Editing Shortlist Handoff
UI Screenshot Structure Review and Development Handoff

© 2026 Elysia Tools. All rights reserved.

DocsPricingAboutTerms of ServicePrivacy PolicyCookiesContact
Python

Web Image Processing Python Samples

Web Python image processing examples using PIL/Pillow including reading, saving, resizing, and format conversion

Media

Copyright-Free FLAC Audio Samples

Lossless FLAC audio samples for testing and development, mirrored from MP3 set with nature sounds and meditation music

Media

Copyright-Free WAV Audio Samples

Uncompressed PCM WAV audio samples for testing and development, mirrored from MP3 set with nature sounds and meditation music

Java

Android Image Processing Java Samples

Android Java image processing examples including reading/saving images, scaling, and format conversion

Education

Absorbance↔Transmittance Converter (A = −log₁₀T)

Convert A ↔ %T ↔ T with A = −log₁₀(T) and %T = 100·T; returns all three representations for spectrophotometry work.

Education

Enzyme Activity Unit Converter (U ↔ katal)

Converts activity values exactly between U/mU/µU and katal/mkat/µkat/nkat/pkat (1 U = 16.67 nkat, 1 kat = 6×10⁷ U). Educational use only.

Education

OD600 Cell Density Calculator (E. coli)

OD600 turbidity to cells/mL (1×10⁹ per OD default) and cell dry weight g/L (0.36 per OD, BioNumbers 109837), normalized for dilution factor and path length, with total cells/CDW from the culture volume, per-cell pg CDW, and an OD > 1 linearity flag. Editable strain-specific factors. Agilent/VectorBuilder/BioNumbers derived. Educational use only.

Education

Protein–DNA Binding Affinity Calculator (Kd Estimate)

Single-point 1:1 Kd estimate: Kd = [P] × (1−f)/f from a direct fraction or anisotropy-derived fraction, plus ΔG° = RT·ln(Kd) and affinity bands from very tight (<1 nM) to weak (>1 µM). Cantor & Schimmel / Heyduk & Lee / Lakowicz derived. Educational use only.

Calculates a molar extinction coefficient ε = 24,000 M⁻¹cm⁻¹.

3. Measuring Protein Concentration in a Short-Path Cuvette

Lab Technician

Background

A purified protein with ε = 45,000 M⁻¹cm⁻¹ reads an absorbance of 0.450 using a 2 mm path length cuvette.

Problem

Compute the micromolar concentration of the protein stock.

How to use

Set Solve For to 'Concentration', select 'uM' as the concentration unit, enter Absorbance as 0.45, Extinction Coefficient as 45000, and Path Length as 2 with unit 'mm'.

Outcome

Calculates the sample concentration as 50.0000 µM.