What a dissolution test is, how % drug release is calculated, how Stage 1, 2 and 3 are decided from the Q value, and what every field, result and message in the Dissolution Calculator means.
Every vessel you enter, one peak area or one absorbance reading, goes through the same calculation:
| Part | Where it comes from |
|---|---|
| Sample Response | The area (HPLC) or absorbance (UV-Vis) you type for that vessel |
| DF | The one combined dilution factor from your SOP. Use 1 if the sample is injected without further dilution |
| Std Potency | From the standard's certificate of analysis, typed as a percentage such as 99.8 |
| Std Weight | Weight of the standard in mg |
| Factor | Optional API factor. Blank, zero or negative counts as 1 |
| Final Std | Mean of your System Suitability readings, or the average of that mean and the covering mean if Covering Standard is on |
| Label Claim | Strength per tablet or capsule, in mg |
The amount released from each vessel in mg is its % Release ÷ 100 × label claim, and the results table shows it to three decimal places. The dissolution medium volume, for example 900 mL, is not part of the formula. It is carried to the printed report for reference only, because the dilution factor is supposed to include it.
Single Time-Point mode, HPLC, Q = 80.0. Standard weight 22.5 mg, potency 99.8%, dilution factor 20, label claim 500 mg, medium volume 900 mL, no factor. Five standard injections: 1201500, 1203900, 1202300, 1204800 and 1202100.
Final Std = 1202920 (the mean of the five). SD = 1375.50 and %RSD = 0.11%. Now the six vessels:
| Vessel | Area | % Release | Amount (mg) | Status at Stage 1 (≥ 85.0%) |
|---|---|---|---|---|
| 1 | 1201000 | 89.68% | 448.383 | Pass |
| 2 | 1213400 | 90.60% | 453.013 | Pass |
| 3 | 1189700 | 88.83% | 444.164 | Pass |
| 4 | 1207800 | 90.18% | 450.922 | Pass |
| 5 | 1195200 | 89.24% | 446.218 | Pass |
| 6 | 1219600 | 91.07% | 455.327 | Pass |
For vessel 1: (1201000 × 20 × 0.998 × 22.5 × 100) ÷ (1202920 × 500) = 89.68%. The summary row shows mean 89.93%, minimum 88.83%, maximum 91.07%, SD 0.84 and %RSD 0.94%. With 6 vessels the stage label reads Stage 1 (S1) — n = 6. Every vessel is at or above Q + 5% (85.0%), so the time point passes.
Change vessel 3 to an area of 1110500. Its result falls to 82.92%, which is below 85.0%, so Stage 1 fails even though the mean (88.95%) is far above Q. Now add six more vessels at the same time point with areas 1198900, 1205100, 1202300, 1192600, 1210400 and 1199800. With 12 vessels the label becomes Stage 2 (S2) — n = 12. The mean is 89.33%, which is at least Q, and the lowest vessel (82.92%) is above Q − 15% (65.0%), so the time point passes at Stage 2.
Look at the %RSD of that 12-vessel set: 2.35%. If your %RSD limit is still at its starting value of 2.0, that card turns red with an Exceeds limit label, while the verdict stays PASS, because %RSD never changes the verdict.
The stage is chosen by how many vessels at that time point have a valid reading. You do not select it. The calculator then applies one rule set:
| Vessels | Stage shown | Pass condition | With Q = 80 |
|---|---|---|---|
| 1 to 6 | Stage 1 (S1) | Every vessel ≥ Q + 5% | Every vessel ≥ 85.0% |
| 7 to 12 | Stage 2 (S2) | Mean ≥ Q, and no vessel below Q − 15% | Mean ≥ 80.0%, none below 65.0% |
| 13 or more | Stage 3 (S3) | Mean ≥ Q, and no vessel below Q − 15% (the calculator also reports Q − 25%) | Mean ≥ 80.0%, none below 65.0% |
In the results table each vessel gets its own Pass or Fail flag against the stage threshold (Q + 5% for Stage 1, Q − 15% for Stage 2, Q − 25% for Stage 3), and the summary row gives the stage verdict. The small column before % Release, labelled vs Q-Value, simply shows how far each vessel is from Q itself, for example +9.7%.
Enter six vessels first. If the time point fails, and your procedure allows continuing, test six more units and add them as extra rows at the same time point, so the calculator sees 12. Then, if needed, add twelve more to reach 24. The calculator judges the whole set each time, not just the new vessels.
| Field | What to know |
|---|---|
| Instrument Type | HPLC (peak area) or UV-Vis (absorbance). Placeholders, headings and the note beside each time point change to match. |
| Absorbance Range | UV-Vis only. No default; you must choose one before calculating. |
| Standard Weight (mg) | Required. Accepts 0.001 to 100000. |
| Standard Potency / Purity (%) | Required. Accepts 0.001 to 100, so type 99.8, not 0.998. |
| Dilution Factor | Required. Accepts 0.000001 to 10000. |
| Dissolution Medium Volume (mL) | Reference only. Not used in the calculation and not required. |
| Label Claim (mg per unit) | Required. Accepts 0.001 to 100000. |
| API Factor | Optional. Leave blank if it does not apply. When it is used, the printed formula includes it. |
| Q-Value (%) | Starts at 80.0. Accepts 0 to 100. If left blank or zero, 80 is used. |
| %RSD Acceptance Limit | Starts at 2.0. Informational only; it colours the %RSD card and does not affect the verdict. |
| Standard System Suitability | Five rows to begin with. Add or remove rows. Only values above zero count. |
The line under the standard readings shows the count, mean, SD and %RSD as you type. The standard's own %RSD is also flagged in the calculation breakdown with a tick when it is 2.0% or less and a warning otherwise.
Two buttons control this. Without Covering Standard is the default and every time point uses the System Suitability mean. With Covering Standard adds a Covering Standard Readings block to every time point, with two empty rows to start, and you can add more.
For a time point with covering readings, the standard used is the average of two numbers, not of all readings together:
If the five standard injections above average 1202920 and two covering readings of 1206200 and 1205400 average 1205800, the Final Std for that time point is (1202920 + 1205800) ÷ 2 = 1204360. A line under the covering rows spells out this working as you type. If a time point has no covering readings yet, its Final Std is just the System Suitability mean. Each time point keeps its own covering readings, so they never leak into another time point's calculation.
| Option | Allowed absorbance | Description in the form |
|---|---|---|
| 0.2 – 0.8 | 0.2 to 0.8 | Ideal range for highest accuracy |
| 0.2 – 1.0 | 0.2 to 1.0 | Preferred working range |
| 0.00 – 2.00 | 0.00 to 2.00 | Acceptable if method validation supports it |
Every absorbance in the standard, covering and vessel boxes is checked against the chosen range. One value outside it blocks the whole calculation, outlines the box in red, and shows a message naming the range. Values are not dropped silently. Switching back to HPLC hides the range selector and clears the selection, so you have to pick again the next time you go to UV-Vis.
Results disappear the moment you change any field, so a number on screen always matches the data in the form. Press Calculate Dissolution again after an edit.
| Situation | What happens |
|---|---|
| UV-Vis selected, no absorbance range chosen | A message appears and the range drop-down is highlighted. |
| An absorbance outside the chosen range | Outlined in red, with a message naming the range. |
| Standard weight, potency, dilution factor or label claim missing, zero or out of range | The message names the field and the cursor jumps to it. |
| No standard reading above zero | A message asks for at least one valid standard value. |
| No vessel with a valid response | A message asks for at least one vessel with a valid response. |
Empty vessel rows are skipped, so you do not need to delete the ones you did not use. Only positive responses count. The calculator also ignores clicks that come within 0.8 seconds of the previous calculation.
Copy Report copies a plain-text report: a title line, the standard %RSD, the inputs, a summary line for every time point (mean, min, max, SD, %RSD, stage and verdict) and the final summary. A message confirms when it has been copied.
Print Report works only after a calculation. It opens an editable A4 sheet, and a long report can run onto several pages with the letterhead and signature block repeating. The following are filled in for you and locked, so the sheet cannot disagree with the calculation: standard potency, standard weight, dilution factor, medium volume, and the method (HPLC or UV-Vis). The System Suitability table, with average, SD and %RSD, and one block per time point (vessel readings, % dissolved, average, min, max, SD, %RSD and a PASS or FAIL line with the stage and Q) are filled in too. Any covering standard readings used at a time point are listed in that time point's block.
You type the rest directly on the sheet: batch number, analysis date, reason for testing, testing frequency, API, manufacturer of API, storage condition, instrument name and traceability, working standard reference number, and sampling time, plus the Analyzed by and Checked by lines.
For a logo, use a PNG, JPG or WebP image that is perfectly square (equal width and height), between 30 × 30 and 1000 × 1000 px, and no larger than 1 MB. Rectangular logos are rejected here. Choose Save as PDF in the print dialog and switch off Headers and footers for the cleanest file. Esc closes the preview.
Q is the amount of drug, as a percentage of the label claim, that must be dissolved at the specified time. It comes from your monograph or specification, for example Q = 80% at 30 minutes. In the calculator it is the Q-Value field, which starts at 80.0. Every stage check is built from Q: Stage 1 uses Q + 5%, and Stages 2 and 3 use Q for the mean and Q − 15% for the lowest allowed unit.
They are the three testing stages of USP <711>, using 6, then 12, then 24 units. The calculator does not ask you which stage you are at. It counts the vessels with a valid reading at each time point: 6 or fewer is treated as Stage 1, 7 to 12 as Stage 2, and 13 or more as Stage 3. To move on from a failed Stage 1, add six more vessels to the same time point and calculate again.
% Release = (Sample Response × Dilution Factor × (Standard Potency ÷ 100) × Standard Weight × Factor × 100) ÷ (Final Standard Response × Label Claim). Sample Response is the peak area for HPLC or the absorbance for UV-Vis. Factor is optional and counts as 1 when left blank. The amount released in mg is the % Release divided by 100 and multiplied by the label claim.
A failing Stage 1 does not end the test. Check the weighing, dilution and transcription first. If the data are right and your procedure allows it, test six more units, add them as additional vessels at the same time point so the total is 12, and calculate again. The result is then judged as Stage 2: the mean of all 12 must be at least Q and no unit may be below Q − 15%. If that fails, six more vessels would be added to make 24.
No. The %RSD of the vessels is shown for every time point and turns red with an Exceeds limit label when it is above your %RSD limit, but the PASS or FAIL verdict comes only from the stage rules, or from your custom limits when you set them. The %RSD limit field starts at 2.0 and is informational, so use your own SOP to decide what a high value means.
When you switch it on, each time point gets its own Covering Standard readings block. The standard used for that time point becomes the average of two numbers: the System Suitability average and the covering average. It is not an average of every reading mixed together. Switch it off and every time point uses the System Suitability average on its own.
Yes. Each time point has a Min Limit and a Max Limit box. If either is filled with a value above zero, the Q-based stage logic is replaced for that time point. The result is labelled Custom Limits, and every vessel must be at or above the minimum and at or below the maximum. Both boxes accept 0 to 200.
Because the dilution factor you enter is meant to include it. The calculator uses the medium volume only for documentation: it appears on the printed report and is not part of the formula and is not required to calculate. If you do not know your dilution factor, the Dilution Factor calculator on this site can work it out.
The calculator offers 0.2 to 0.8 (ideal), 0.2 to 1.0 (preferred) and 0.00 to 2.00 (acceptable if your method validation supports it). You have to choose one before calculating. Every absorbance you type, in the standard, covering and vessel boxes, must sit inside it, otherwise the calculation stops and the offending boxes are outlined.
Yes, choose Multi Time-Point Profile. Each time point has its own minutes box, its own vessels, its own limits and its own verdict. The overall banner reads PASS only if every time point passes, and a bar chart of the mean % release against time appears once you have more than one.
The calculation, results, copy text and print preview all run in your browser, and the calculator script does not send your entries to a server.
Educational use only. This guide explains how the Dissolution Calculator on this site works. It is not a validated system and does not replace your SOPs, your monograph or the pharmacopoeial text. See the Dissolution Test theory and guidelines page for background and the disclaimer for how to use this site.
Dissolution Test — Theory & Guidelines
System Suitability %RSD & %CV
Standard Check Calculator
Dilution Factor Calculators
Comparative Dissolution Profile Calculators
AMV Calculators — Analytical Method Validation & Verification