A protein concentration calculator is a tool that converts experimental measurements (mass, volume, absorbance, or dilution parameters) into precise protein concentration values and visualizes those results.

How this protein concentration calculator works

This calculator provides three common workflows: direct mass/volume conversion (mg per mL), Beer–Lambert absorbance-based molar concentration, and a practical dilution calculator for making working solutions from a stock. It’s built to run inside a WordPress custom code block, sized responsively to fit between sidebars with a clean white background, and includes an interactive Plotly.js chart to visualize results.

Which calculation should you choose?

• Mass/Volume: Use when you know the mass of protein and the final volume. The tool returns mg/mL, µg/µL and mg/L.
• Beer–Lambert: Use when you have an absorbance measurement. Enter absorbance, molar extinction coefficient (ε, M⁻¹cm⁻¹) and pathlength in centimeters; the calculator computes molar concentration using C = A / (ε·l) and converts to mg/mL when the protein molecular weight is provided.
• Dilution: Use when preparing working concentrations from a stock solution. Enter stock concentration, desired concentration, and desired final volume; the tool computes the required stock volume and diluent volume.

Step-by-step: using the tool (quick guide)

1. Paste the provided HTML/JavaScript into a WordPress custom HTML block or theme file. The component is responsive and will expand to the content column width.
2. Choose the calculation type from the dropdown.
3. Fill in the required inputs for that mode — the form fields update dynamically.
4. Click “Calculate”. The numeric results appear immediately and Plotly renders an interactive bar chart showing the measured or calculated concentrations and volumes.
5. Use the “Copy Result” button to quickly paste values into a lab notebook or inventory system. If you need a serial dilution series, set the number of steps for a quick visual guide.

Important units and conversions

Accurate units are crucial. Common pitfalls:

• Pathlength should be in cm (typical cuvette: 1 cm; some plate readers: 0.5 cm or variable).
• Extinction coefficient ε is in M⁻¹·cm⁻¹ for Beer–Lambert.
• Molecular weight (MW) in Daltons (g·mol⁻¹) for conversion between molar concentration and mass concentration.

Example conversions performed by the tool: mol/L to mg/mL: (mol/L) × (MW g·mol⁻¹) / 1000.

Why Plotly.js?

Plotly provides an interactive, embeddable chart that works in WordPress without additional build steps. In this tool, Plotly renders:

• A concentration comparison bar chart (e.g., stock vs target vs calculated).
• Optional serial dilution series when multiple steps are requested.

Interactivity helps spot errors: hover to see precise values, zoom, and save charts.

Best practices and tips

• Validate extinction coefficients: use values from vendor data sheets or primary literature. For proteins without known ε, use 1 mg/mL ≈ 1 A280 unit for rough estimates — but treat this as approximate.
• For plate readers with variable pathlength correction, either input the effective pathlength or correct absorbance beforehand.
• When preparing dilutions, pipette volumes smaller than 2 µL are error-prone; scale up volumes proportionally if required.
• Keep units consistent. The tool will flag inconsistent or missing inputs.

Example workflows

1. Mass/Volume: You have 5 mg of protein dissolved in 2 mL. Select Mass/Volume, enter mass=5 mg and volume=2 mL. Result: 2.5 mg/mL (also 2500 mg/L and 2.5 µg/µL).
2. Beer–Lambert: Absorbance at 280 nm = 0.85, ε = 44000 M⁻¹cm⁻¹, pathlength = 1 cm, MW = 66,000 g·mol⁻¹. The tool computes molar concentration ≈ 1.93×10⁻⁵ M and mass concentration ≈ 1.27 mg/mL.
3. Dilution: Stock 10 mg/mL, target 0.5 mg/mL, final volume 10 mL. Stock volume required = (C2·V2)/C1 = 0.5×10 / 10 = 0.5 mL; add 9.5 mL diluent.

Limitations and accuracy

This calculator assumes ideal behavior and accurate input data. Factors that will affect accuracy include:

• Inaccurate absorbance readings (dirty cuvettes, bubbles).
• Incorrect extinction coefficients or molecular weight values.
• Nonlinear absorbance at high concentrations (deviation from Beer–Lambert law).

Always validate critical concentrations experimentally.

Security and privacy

All calculations run in the browser; no data is transmitted to servers. This keeps sensitive experimental data local to your computer.

Troubleshooting

• If the chart does not render, ensure Plotly.js CDN is reachable and not blocked by your hosting provider.
• If numbers look off, double-check units and molecular weight entries.
• For mobile view, the layout stacks inputs above the chart.

Additional practical tips: always label tubes with concentration and date, use calibrated pipettes, run a blank control for absorbance measurements, and when possible, verify concentrations with an orthogonal method such as SDS-PAGE densitometry or amino acid analysis for high-precision needs. Regularly record lot numbers for reagents and instruments to trace sources of variability. Contact your laboratory manager for recommended extinction coefficients, standard reference materials, and institution-specific SOPs when in doubt please consult.

FAQ

Q: Can the tool convert from A280 directly to mg/mL without MW?
A: The tool can provide approximate conversions using typical protein assumptions (e.g., 1 A280 ≈ 1 mg/mL) but recommends supplying molecular weight for accurate results.

Q: Is the pathlength always 1 cm?
A: No. Standard cuvettes are 1 cm, but microvolume devices and plate readers have different effective pathlengths; input the correct pathlength for accurate Beer–Lambert calculations.

Q: Can I print or export the chart?
A: Yes. Use the Plotly toolbar on the chart to download a PNG. You can also copy numeric results with the “Copy Result” button.

Q: Does the calculator handle serial dilutions?
A: Yes. The dilution mode supports creating a simple serial dilution series for visualization; it will provide volumes for each step.