A bottle of oral liquid is labelled in millilitres, and the dose is too, so how long it lasts is a division most people do on the back of the box. Put in the numbers from the bottle and the label, and this gives the full doses, the days, and the date it runs out.
Liquid medicine days
Bottle ml → doses and run-out date
The bottle and the label
Nothing you type here leaves your browser.
Why a bottle runs out early
Some liquid always stays in the bottle neck, on the syringe and on the spoon, so a 100 ml bottle rarely gives exactly 100 ml of doses. Treat the date here as the latest it could last, and get the next bottle a few days before it.
Measure with the device that came with it
Kitchen teaspoons vary a lot in size. Use the oral syringe or cup supplied with the medicine, in ml, and take the ml per dose from the label or your prescriber. This page does not convert between ml and any other unit, and it will not work out a dose.
Check the use-by after opening
Many liquids have to be thrown away a set number of days after opening, whatever is left. If that date comes before the one here, the use-by date wins. The label or your pharmacist will tell you which applies.
The same arithmetic for tablets is the days supply calculator, and for puffs the inhaler days calculator. If a pack has to cover a trip, the packing write-up walks through the extra days worth adding.
Common questions
How long does a 100 ml bottle last at 5 ml twice a day?
5 ml twice a day is 10 ml a day, so 100 ml holds 20 doses and lasts 10 days. In practice a little stays in the bottle and on the syringe, so get the next one a few days early.
How many 7.5 ml doses are in a 100 ml bottle?
13 full doses. 13 doses use 97.5 ml, and the 2.5 ml left over is not enough for a 14th full dose.
Can this calculator convert mg to ml?
No. It only divides the ml in the bottle by the ml per dose on your label. Converting between mg and ml depends on the strength of the specific product, and that is a question for your pharmacist.
One thing this cannot do
This is an arithmetic tool, not medical advice. It works out numbers from what you type in — it does not know your medication, your prescription, or what you should do if something goes wrong. Anything about changing a dose, spacing doses differently, or handling a missed dose is a question for your doctor or pharmacist.