Protein Yield Calculator
FREE TOOLEnter data for each purification step. The first row should be the crude lysate (Step 1). All subsequent rows are purification steps (e.g. ammonium sulfate precipitation, affinity chromatography, etc.).
| # | Step Name | Total Volume (mL) | Protein Conc. (mg/mL) | Activity (units/mL) |
|---|
Activity units/mL = enzyme activity per mL (e.g. nmol/min/mL, U/mL). Leave blank if you only want yield/recovery without specific activity.
📈 Protein Purification Table
| Step | Total Vol (mL) | Total Protein (mg) | Total Activity (units) | Specific Activity (units/mg) | Yield (%) | Purification Fold |
|---|
Introduction
Every protein purification protocol trades yield for purity. As you take crude lysate through precipitation, chromatography, and polishing steps, some target protein is inevitably lost — but what remains should become progressively more concentrated in target activity. The Protein Yield Calculator turns your step-by-step volume, concentration, and activity measurements into a complete purification table, so you can see exactly how much protein and activity survive each step, and how much purer your final product is compared to where you started.
This is the same table format used in purification papers and lab notebooks: total protein, total activity, specific activity, percent yield, and purification fold, calculated automatically from the raw numbers you already record during a purification run.
About the Tool
This calculator builds a multi-step protein purification table from the volume, protein concentration, and (optionally) enzyme or biological activity measured at each stage of your protocol — crude lysate, precipitation, chromatography, and any polishing steps you run. It computes total protein, total activity, specific activity, percent yield relative to Step 1, and purification fold relative to Step 1, then visualises recovery with a colour-coded bar chart.
It works entirely in your browser — no data is uploaded or stored — and supports any number of steps, from a simple two-step prep to a full five- or six-column purification scheme.
Input Explanation
Each row in the input table represents one step of your purification, in the order you performed them:
- Step Name: A label for the step (e.g. "Crude Lysate", "Ammonium Sulfate Precipitation", "Affinity Chromatography"). Purely descriptive — it does not affect the calculation.
- Total Volume (mL): The total volume of the fraction recovered at that step, not the volume loaded onto a column.
- Protein Conc. (mg/mL): Total protein concentration of that fraction, typically measured by Bradford, BCA, or A280.
- Activity (units/mL): Optional. The activity of your target protein in that fraction, in any consistent unit (U/mL, nmol/min/mL, RFU/mL). Leave blank if you only want total protein tracking without yield or fold.
The first row must always be Step 1 — your starting material (crude lysate or extract) — since every later yield and fold value is calculated relative to it. Use + Add Step to add rows for additional purification steps.
Formula Explanation
The calculator applies these formulas to each step, using total protein and total activity rather than concentrations, since fraction volumes change between steps:
- Total protein (mg) = Protein Conc. (mg/mL) × Total Volume (mL)
- Total activity (units) = Activity (units/mL) × Total Volume (mL)
- Specific activity (units/mg) = Total activity ÷ Total protein — the purity metric; it should rise with each purification step
- Yield (%) = (Total activity at step N ÷ Total activity at Step 1) × 100
- Purification fold = Specific activity at step N ÷ Specific activity at Step 1
Step 1 is fixed at 100% yield and 1× fold by definition, since it is the baseline every other step is measured against. If the Activity column is left blank for every row, the calculator still reports total protein per step, but yield and purification fold require activity data and will not be calculated.
Worked Example
Sample Input
A five-step His-tag affinity purification, using the same values as the calculator's Load Example button:
| Step | Vol (mL) | Conc. (mg/mL) | Activity (units/mL) |
|---|---|---|---|
| Crude Lysate | 100 | 8.5 | 120 |
| Ammonium Sulfate (40–70%) | 40 | 15.2 | 280 |
| Ion Exchange (DEAE) | 20 | 12.4 | 490 |
| Affinity Chromatography (His) | 8 | 6.8 | 1050 |
| Size Exclusion (SEC) | 5 | 5.1 | 1280 |
Step-by-Step Calculation
Step 1 — Crude Lysate (baseline): Total protein = 8.5 × 100 = 850 mg. Total activity = 120 × 100 = 12,000 units. Specific activity = 12,000 ÷ 850 = 14.12 units/mg. Yield = 100% and fold = 1× by definition.
Step 4 — Affinity Chromatography: Total protein = 6.8 × 8 = 54.4 mg. Total activity = 1050 × 8 = 8,400 units. Specific activity = 8,400 ÷ 54.4 = 154.41 units/mg. Yield = (8,400 ÷ 12,000) × 100 = 70.0%. Fold = 154.41 ÷ 14.12 = 10.94×.
The remaining steps follow the same pattern; running all five through the calculator gives:
| Step | Total Protein (mg) | Total Activity (units) | Specific Activity (units/mg) | Yield (%) | Fold |
|---|---|---|---|---|---|
| Crude Lysate | 850.00 | 12000.0 | 14.118 | 100.0% | 1.00× |
| Ammonium Sulfate | 608.00 | 11200.0 | 18.421 | 93.3% | 1.30× |
| Ion Exchange (DEAE) | 248.00 | 9800.0 | 39.516 | 81.7% | 2.80× |
| Affinity Chromatography | 54.40 | 8400.0 | 154.412 | 70.0% | 10.94× |
| Size Exclusion (SEC) | 25.50 | 6400.0 | 250.980 | 53.3% | 17.78× |
Final Result
Starting from 850 mg of total protein and 12,000 units of total activity, the final SEC fraction contains 25.5 mg of protein carrying 6,400 units of activity — a specific activity of 250.98 units/mg, roughly 17.8-fold purer than the crude lysate, with 53.3% of the original activity retained.
Interpretation
The largest single jump in purification fold happens at the affinity chromatography step (from 2.80× to 10.94×), which is typical — affinity capture is usually the most selective step in a His-tag purification. Yield drops steadily but predictably at each step; none of the individual losses (6.7%, 11.7%, 11.7%, 16.7%) signal a problem, since some loss is expected at every physical separation step.
Result Interpretation
The summary cards at the top of your results show starting protein, final protein, final yield, and final purification fold at a glance. The purification table beneath them gives the full breakdown per step, and the recovery bar chart visualises yield step-by-step — green bars (≥70%) indicate a low-loss step, amber (40–69%) a moderate loss, and red (below 40%) a step worth investigating.
A rising specific activity and fold value at every step indicates the purification is enriching your target protein as expected. A flat or falling specific activity at any step means that step removed target activity roughly in proportion to total protein — it isn't purifying, and may be worth reviewing (wrong elution conditions, resin overload, or an inhibitory buffer carried into the activity assay).
Practical Applications
This calculator is used any time a purification protocol needs to be evaluated or reported as a table, including:
- Recombinant protein production QC: Confirming that each step of a His-tag, GST-tag, or ion-exchange purification is actually enriching — not just diluting — your target protein before scaling up.
- Comparing purification protocols: Running two different schemes (e.g. IEX-then-affinity vs. affinity-then-SEC) through the calculator to compare final yield and fold side by side.
- Publication-ready purification tables: Methods sections and supplementary tables in protein biochemistry papers commonly report exactly this table — total protein, activity, specific activity, yield, and fold per step.
- Troubleshooting low-yield preps: Identifying which specific step in a multi-step protocol is responsible for unexpectedly low final yield.
As a rough benchmark, typical values by step type are: crude lysate (100% yield, 1× fold by definition), ammonium sulfate precipitation (70–90% yield, 2–5× fold), ion exchange chromatography (50–80% yield, 5–20× fold), affinity chromatography (40–70% yield, 50–500× fold), and size exclusion polishing (30–60% yield, 100–1000× fold) — though these vary substantially by protein and protocol.
Scientific Notes & Limitations
This tool performs arithmetic on the numbers you enter; it does not measure anything itself, and the accuracy of the output is entirely dependent on the accuracy of your protein concentration and activity assays.
- Protein concentration should be determined by a consistent method (Bradford, BCA, or A280) across all steps — switching assay methods partway through a purification introduces systematic error the calculator cannot detect.
- Activity assays must use the same substrate, conditions, and units at every step. Buffer components carried over between steps (imidazole, high salt, detergents) can inhibit or artificially inflate an activity readout.
- The calculator assumes activity and protein measurements are linear within the assay range used; readings taken outside a validated linear range will distort specific activity and fold values.
- Results reflect only the numbers entered — they do not account for storage-related activity loss, freeze-thaw degradation, or day-to-day assay variability between purification runs.
Practical Tips
- Record total volume, not concentration alone, at every step. Total protein and total activity depend on volume, so a concentration-only record can't reconstruct the table later.
- Run a no-activity control if using a coupled or chromogenic assay, so buffer interference doesn't get misread as a change in specific activity.
- Measure activity and protein concentration from the same aliquot whenever possible, to avoid step-to-step sampling error affecting the specific activity ratio.
- Use the bar chart to catch outlier steps early. An unexpected red bar partway through a run is often easier to diagnose immediately than after the whole purification is finished.
Common Mistakes
- Mixing up loaded volume and recovered volume: Total Volume should be the volume of the fraction you recovered at that step, not the volume you loaded onto a column or resin.
- Unit inconsistency: Entering concentration in µg/mL when the tool expects mg/mL (or activity in different units between steps) will silently produce wrong yield and fold values with no error message.
- Treating a low-yield step as a failure: Some loss is normal and expected at every physical separation step. Compare against typical yield ranges for that step type before concluding something went wrong.
- Ignoring a flat or falling purification fold: If specific activity doesn't increase at a step, that step is not purifying your target — investigate elution conditions or assay interference rather than proceeding to the next step.
Frequently Asked Questions
Yield tells you how much of the original target activity you still have (as a percentage of Step 1). Purification fold tells you how much purer the sample is — how enriched the target protein is relative to everything else in the mixture. A step can have low yield but high fold (you lost a lot of material, but what remains is very pure), or high yield with low fold (you kept almost everything, but didn't remove much contaminant).
No. If you leave the Activity column blank, the calculator still reports total protein at each step and the recovery bar chart based on total protein. Yield (%) and purification fold specifically require activity data, since both are defined relative to enzymatic or biological activity, not just protein mass.
A fold value below 1× means the specific activity (units/mg) at that step is lower than it was at Step 1 — the step diluted or degraded the target activity relative to total protein, rather than enriching it. This can happen with a poorly optimized wash step, protein aggregation, or an inhibitory buffer component carried over into the activity assay.
Use total volume in mL, protein concentration in mg/mL, and activity in units/mL (any consistent activity unit works, e.g. U/mL, nmol/min/mL, or RFU/mL). As long as every row uses the same units, the calculated yield percentages and fold values remain valid.
Yes. Use the + Add Step button to add as many rows as your protocol needs, and − Remove Step to delete the last row. All calculations are still made relative to Step 1, regardless of how many steps you add.
Step 1 is the reference point for every other calculation in the table — it represents your starting crude extract before any purification. Every later step's yield and fold are expressed relative to this baseline, so Step 1 is fixed at 100% yield and 1× fold by definition.