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: September 2026
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About this calculator
Converting a mg dose to mL for a liquid medication requires the solution's concentration. Volume (mL) = dose (mg) / concentration (mg/mL). Concentration is usually printed on the label as "amount per volume" (e.g. 250 mg per 5 mL = 50 mg/mL).
Common concentrations: amoxicillin oral suspension comes in 125 mg/5 mL (25 mg/mL), 200 mg/5 mL (40), 250 mg/5 mL (50), and 400 mg/5 mL (80). Acetaminophen infant drops are 100 mg/mL — a much higher concentration than the 32 mg/mL children's suspension, and mixing them up is a common pediatric overdose.
Pediatric dosing typically uses mg per kg body weight: dose_mg = mg_per_kg × weight_kg, then divide by concentration to get mL. Always measure with a calibrated oral syringe, not a kitchen spoon — kitchen teaspoons vary from 3 to 8 mL. Ask the pharmacist for a syringe if the bottle doesn't include one.
How to use
Example — 250 mg dose at 50 mg/mL (250 mg / 5 mL suspension). Volume = 250 / 50 = 5 mL. That is one teaspoon of the standard 250 mg / 5 mL antibiotic. Example — the same 250 mg dose at 100 mg/mL (a concentrated pediatric drop). Volume = 250 / 100 = 2.5 mL. Much smaller volume; use a 3 mL oral syringe. A 5 mL teaspoon of 100 mg/mL drops would deliver 500 mg — twice the intended dose. Concentration errors are a leading pediatric medication error.
Frequently asked questions
Why does concentration matter?
Because a 5 mL teaspoon of a 50 mg/mL suspension delivers 250 mg, but 5 mL of a 100 mg/mL concentrate delivers 500 mg — a 2× overdose. The mg dose is what matters therapeutically; the mL is just the volume needed to deliver it at the specific concentration on hand.
What if my label shows mg per 5 mL?
Divide by 5 to get mg/mL. So "125 mg per 5 mL" = 25 mg/mL. Use that concentration in the calculator. Most US pediatric liquids are labeled "per 5 mL" (one teaspoon) rather than per mL.
Are these results safe to dose from?
This is a math tool, not a clinical decision. Always verify against the prescription and the label, use an oral syringe (not a kitchen spoon), and call the pharmacist or prescriber if anything is unclear. Pediatric dosing errors are a common cause of ER visits.
Do injectable medications use the same conversion?
Same math, different unit vigilance. IV concentrations are often much higher (potassium 2 mEq/mL, insulin 100 units/mL) and errors are catastrophic. Bedside verification with a second nurse is standard practice for high-alert medications.