mg to mL Calculator (with Concentration)
Convert a mg dose to mL (or mL back to mg) using a solution concentration. Preset picks for common pediatric and adult liquid medication concentrations.
Last updated: October 2026
Volume or mass
5 mL
Formula below · 2 sources (fda.gov, accessdata.fda.gov) · Updated Oct 2026
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About this calculator
To convert a dose in mg to mL, divide the dose by the liquid's concentration in mg per mL: 100 mg of a 100 mg/5 mL suspension (20 mg/mL) is 100 ÷ 20 = 5 mL. Going the other way, multiply the volume by the concentration: 5 mL × 20 mg/mL = 100 mg. There is no fixed mg-to-mL conversion, because milligrams measure the drug and milliliters measure the liquid it is dissolved or suspended in.
Reading the concentration from the label
U.S. labels usually state strength as an amount per 5 mL. Divide by 5 to get mg/mL: 250 mg/5 mL is 50 mg/mL and 160 mg/5 mL is 32 mg/mL. If the label already says "per mL," use the number as is. Pick a preset that matches your label, or type the exact strength in the custom box, which overrides the preset when filled.
Why the concentration matters
The same drug can come in several strengths. Amoxicillin oral suspension, for example, is labeled at 125, 200, 250 and 400 mg per 5 mL, so 5 mL can contain anywhere from 125 to 400 mg. The FDA moved children's and infants' over-the-counter liquid acetaminophen to a single 160 mg/5 mL strength after mix-ups between it and the older, more concentrated infant drops (80 mg/0.8 mL) led to overdoses. Always check the strength on the bottle you are actually using.
Measuring the dose
Use the oral syringe or dosing cup that comes with the medicine and that is marked in mL, not a kitchen spoon. This calculator does arithmetic only: it does not choose a dose, check a dose against weight or age, or replace the instructions from your prescriber or pharmacist.
| Product (FDA labeling) | Labeled strength | mg per mL | Volume for 100 mg |
|---|---|---|---|
| Acetaminophen, children's and infants' OTC liquid (U.S., since 2011) | 160 mg / 5 mL | 32 | 3.1 mL |
| Acetaminophen infant drops (discontinued in U.S.) | 80 mg / 0.8 mL | 100 | 1 mL |
| Amoxicillin oral suspension | 125 mg / 5 mL | 25 | 4 mL |
| Amoxicillin oral suspension | 200 mg / 5 mL | 40 | 2.5 mL |
| Amoxicillin oral suspension | 250 mg / 5 mL | 50 | 2 mL |
| Amoxicillin oral suspension | 400 mg / 5 mL | 80 | 1.25 mL |
How to use
Choose the direction (mg → mL or mL → mg), enter the amount, and pick the concentration preset that matches the strength printed on your label. If your strength is not listed, type it in mg/mL into the custom box; a filled custom value is used instead of the preset. The default, 100 mg at 100 mg/5 mL (20 mg/mL), gives 5 mL. Always confirm the result against the prescription and the label.
Frequently asked questions
How many mL is 100 mg?
It depends on the concentration. At 20 mg/mL (100 mg per 5 mL) it is 5 mL; at 32 mg/mL (160 mg per 5 mL) it is about 3.1 mL; at 50 mg/mL (250 mg per 5 mL) it is 2 mL. Divide the mg dose by the mg/mL strength on your label.
What if my label shows mg per 5 mL?
Divide the mg figure by 5 to get mg/mL. For example, 125 mg per 5 mL is 25 mg/mL and 400 mg per 5 mL is 80 mg/mL. Enter that number as the concentration.
Are infant and children's liquid acetaminophen the same strength?
In the United States, over-the-counter liquid acetaminophen for children under 12, including infants' products, is now sold at one strength, 160 mg per 5 mL. Older concentrated infant drops (80 mg/0.8 mL) were discontinued because confusion between the strengths caused overdoses. Check any older bottle carefully before use.
Are these results safe to dose from?
This is a unit-conversion tool, not medical advice. Verify every dose against the prescription and the product label, measure with an mL-marked oral syringe or the cup supplied with the medicine, and ask a pharmacist or prescriber if anything is unclear.
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