Compare the ratio, not the biggest printed number
“50 mg per 5 mL” and “20 mg per 2 mL” both divide to 10 mg/mL. The first numerator is larger, but its denominator is larger by the same factor. Comparing 50 with 20 on its own would miss that relationship.
Concentration ratio = concentration A ÷ concentration B
The comparison starts with two complete pairs. For just one label, the concentration label helper provides a focused normalization tool. If you already know the concentration and need to convert a known mass or volume, use the mg to mL converter.
Use the same ingredient basis
The values must describe the same named ingredient and the same chemical form. A mass given for a salt, a base or an equivalent active component can have a different basis. This app does not resolve those differences from the numbers. The confirmation checkbox asks you to check them before comparing.
Equal mg/mL values do not establish equal ingredients, formulation, quality, route of use or suitability. A concentration calculation cannot determine whether two products are interchangeable. For a medication label that is unclear, ask a pharmacist to identify the stated basis.
Mass and volume units change independently
The app supports mg, mcg and g for ingredient mass, and mL or L for volume. A milligram is 1,000 micrograms; a gram is 1,000 milligrams; a liter is 1,000 milliliters. Each side is normalized independently before comparison.
| Original label ratio | Mass and volume in mg and mL | Concentration |
|---|---|---|
| 0.2 g per 0.1 L | 200 mg per 100 mL | 2 mg/mL |
| 2,000 mcg per 1 mL | 2 mg per 1 mL | 2 mg/mL |
| 10 mg per 5 mL | 10 mg per 5 mL | 2 mg/mL |
Enter numbers without thousands separators, such as 2000. Changing a unit clears its associated value so a retained number cannot silently acquire a new meaning.
Why the percentage depends on the reference
Label B is the reference throughout this tool. If A is 15 mg/mL and B is 10 mg/mL, A ÷ B is 1.5, so A is 50% higher than B. If the labels are reversed, 10 ÷ 15 is about 0.666667, so A is 33.3333% lower than B.
This is a directional comparison, not the symmetric “percent difference” formula that uses the average of both values. The displayed subtraction A − B also retains its sign. Both concentrations must be positive; a zero reference would make the ratio undefined.
Information that cannot fill a missing label ratio
- Package volume: “100 mL bottle” says how much liquid the package holds, without naming its ingredient concentration.
- Bare percentages: % w/v, % w/w and % v/v describe different bases. Use the confirmed w/v percentage tool only when that basis is stated.
- Whole-liquid density: it counts the entire mixture, not one ingredient. See the concentration versus density guide.
Results show up to six significant figures, while calculations use unrounded values. Values equal within relative floating-point rounding are shown as the same numerical concentration; this is not a measurement-uncertainty allowance. Editing a label or unchecking its basis clears the previous result.
Browse concentration tools and guides →
References and feedback
Strength-expression bases: FDA strength conversion guidance. Metric scale factors: BIPM SI prefixes. These sources explain units and label bases; they do not endorse this app.
Reviewed September 18, 2026. Inputs are processed in your browser without saved entries. Send questions or corrections to contact@mgtoml.app.