mg to mL calculator
Enter the concentration from your own packaging. There is no universal mg to mL conversion.
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A label reading 160 mg / 5 mL is 32 mg per mL.
How do you convert mg to mL?
Divide the dose in milligrams by the concentration in milligrams per millilitre. If a medicine is 160 mg per 5 mL, that is 32 mg/mL, so a 240 mg dose is 240 ÷ 32 = 7.5 mL. Without the concentration the conversion is impossible, because milligrams measure mass and millilitres measure volume.
There is no universal conversion, and there never will be
This is the single thing worth understanding, and the reason most search results for this question are unhelpful.
A milligram measures mass. A millilitre measures volume. Asking how many millilitres are in 500 milligrams is like asking how many litres are in five kilograms — the answer depends entirely on what the substance is and how concentrated it is.
Five millilitres of children's acetaminophen at 160 mg per 5 mL holds 160 mg of drug. Five millilitres of an adult formulation at 500 mg per 5 mL holds more than three times as much, in an identical-looking spoonful. That difference is why the concentration is not optional.
The conversion
Concentration is the bridge between mass and volume.
concentration (mg/mL) = mass on the label ÷ volume on the label160 mg / 5 mL → 32 mg/mL100 mg / 5 mL → 20 mg/mL250 mg / 5 mL → 50 mg/mLvolume = dose (mg) ÷ concentration (mg/mL)mass = volume (mL) × concentration (mg/mL)
Read the concentration off the bottle in front of you rather than from any list, including the presets on this page. The same medicine is routinely sold at different strengths, and paediatric and adult formulations of an identical drug can differ by a factor of three or more.
That is exactly the situation that produces overdoses: a caregiver measures the volume that was right for the old bottle, from a new bottle at a different concentration.
Worked example: a 240 mg dose at 160 mg per 5 mL
Working out the volume for a prescribed 240 mg dose from a bottle labelled 160 mg per 5 mL.
- Convert the label to mg per mL160 ÷ 5 = 32 mg/mL
- Divide the dose by the concentration240 ÷ 32
- Volume required7.5 mL
- In teaspoons1.5 tsp
7.5 mL of that particular bottle delivers 240 mg.
Use the oral syringe or cup that came with the medicine. A kitchen teaspoon varies between about 3 and 7 mL, which on this dose is the difference between 96 mg and 224 mg.
Where liquid dosing goes wrong
- Using a kitchen spoon instead of the supplied oral syringe or cup
- Carrying over the volume from a bottle at a different concentration
- Confusing millilitres with teaspoons in a written instruction
- Mixing up infant drops and children's suspension, which differ sharply in strength
- Reading a total daily dose as a single dose
If any instruction is ambiguous, a pharmacist will clarify it in under a minute and will not mind being asked.
Assumptions and limits
- Assumes the concentration is uniform and the liquid has been shaken if required
- Does not convert by density — this is a drug concentration, not a substance density conversion
- Presets are illustrative examples, not a substitute for your own label
- Says nothing about what dose is appropriate for any person
- Not suitable for injectable dosing, which requires clinical training
Terms on this page
- Concentration
- How much active ingredient sits in a given volume, written on the label as something like 160 mg per 5 mL. Without it there is no conversion.
- Suspension
- A liquid where the drug is dispersed rather than dissolved. It must be shaken before measuring or the dose will be uneven.
- Oral syringe
- The measuring device supplied with liquid medicine. Kitchen spoons vary between roughly 3 and 7 mL and are not reliable.
Common questions
How many mL is 500 mg?
There is no single answer without a concentration. At 100 mg/mL it is 5 mL; at 250 mg/mL it is 2 mL. Milligrams measure mass and millilitres measure volume, so the concentration printed on your bottle is what connects them.
Where do I find the concentration?
On the bottle or carton, usually written as something like 160 mg / 5 mL or 100 mg per 5 mL. Divide the milligrams by the millilitres to get the mg per mL figure this calculator uses.
Is 1 mg the same as 1 mL?
Only by coincidence, when a liquid happens to be exactly 1 mg/mL. Treating them as equivalent is a serious error — for a 250 mg/mL preparation it would be off by a factor of 250.
Can I use a kitchen teaspoon?
It is not reliable. Kitchen teaspoons vary between roughly 3 and 7 mL, so a dose measured that way can be badly out. Use the oral syringe or dosing cup supplied with the medicine.
Does this work for injections?
No. Injectable dosing involves considerations this tool does not model and requires clinical training. Use it for understanding oral liquid concentrations only.
Where these numbers come from
- Health Canada — Safe use of over-the-counter medicines Guidance on reading medicine labels and safe dosing.
- Canadian Pharmacists Association Pharmacists are the fastest route to confirming any dose question.
Last verified 2026-08-01 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
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