Teaspoon to mL

The 5 mL Dosing Spoon and the One in the Drawer

"One teaspoonful" is one of the most familiar instructions in medicine, and one of the least precise things you can write on a bottle. It names two entirely different objects: a moulded dosing spoon or syringe built to hold 5 mL, and whatever spoon happens to be nearest in the cutlery drawer. Those two hold noticeably different amounts, and the gap between them is where most liquid-medicine measuring errors come from.

Conversion factor: 1 US teaspoon = 4.92892159375 mL exactly, which dosing devices round to a clean 5 mL. So "1½ teaspoons" is 7.393 mL exactly, and appears on a dosing cup as the 7.5 mL line — a rounding of about 1.4 %.

Three Different Things Called a Teaspoon

The defined unit

The US customary teaspoon is a sixth of a fluid ounce: 4.92892159375 mL, fixed by definition. It is the value a converter uses, and the reason a teaspoon figure never lands on a whole number of millilitres.

The device teaspoon

Oral syringes, dosing cups and moulded medicine spoons are made to 5 mL, not 4.929 mL. Every marking on them — 2.5, 7.5, 10, 15 mL — follows from that rounded 5 mL step.

The cutlery-drawer teaspoon

Not a unit at all. Household spoons have been measured across a range of roughly 3 to 7 mL, with outliers from about 1.5 mL up to 9 mL — anything from a third of a "teaspoonful" to nearly two.

The wording steers the choice

Research on parents measuring children's medicine found that when a label spelled out "teaspoon", they were far more likely to reach for a kitchen spoon than a supplied device — which is why mL-only labelling is now recommended.

Turning a Spoon Instruction into a Millilitre Mark

The job is to get from words on an instruction sheet to a line you can see on the device in front of you, without inventing a mark that is not there.

Enter the teaspoon figure as a decimal

Half a teaspoon is 0.5, a teaspoon and a half is 1.5. The millilitre value updates as you type, showing the exact figure rather than the rounded one. A comma works as a decimal separator and spaces are ignored.

Find the nearest real marking

Devices step in 0.5 mL or 1 mL, so 7.393 mL becomes the 7.5 mL line. Never split the difference between two marks by eye — pick the line the device gives you and check it against the label wording.

Take the number with you

The copy button puts the bare figure on the clipboard — no unit, no spaces — handy for a note to a carer, a nursery form or a medicine diary. Ctrl + C inside a field does the same.

Read a millilitre label back in spoons

Press the swap button (↔) to run mL → tsp when the bottle is marked in millilitres but an older leaflet, a relative or a translated instruction still talks in spoonfuls. 10 mL comes back as 2.029 teaspoons — in other words, two.

Information, not instruction. This page converts a unit of volume. It does not tell you how much medicine to take or give, and it cannot check an amount for you. Follow the amount on the label and the advice of your pharmacist, doctor or nurse.

Dosing-Device Markings and the Spoon Words They Replace

Every marking on a modern oral syringe or dosing cup is a rounded stand-in for an old spoon instruction. The middle columns show what the label used to say and what that phrase is worth if you take the teaspoon literally.

Marking on the device	Spoon wording it replaces	Exact US teaspoon value	Where you see the marking
1.25 mL	¼ teaspoon	1.232 mL	Small oral syringe, graduated dropper
2.5 mL	½ teaspoon	2.464 mL	Oral syringe, smallest line on most dosing cups
5 mL	1 teaspoon	4.929 mL	Oral syringe, dosing cup, moulded medicine spoon
7.5 mL	1½ teaspoons	7.393 mL	Dosing cup, 10 mL oral syringe
10 mL	2 teaspoons	9.858 mL	Full barrel of a 10 mL oral syringe, dosing cup
15 mL	1 tablespoon (3 teaspoons)	14.787 mL	Top line on a dosing cup

The rounding is small and consistent: every marking is about 1.4 % larger than the spoon phrase it stands for, which is far below the variation between one household spoon and another. Standardising on 5 mL trades a negligible error for a scale everyone reads the same way.

How the Converter Fits This Job

The exact figure, not the marketing round number

Results carry up to eight decimals, so you see 4.92892159 mL for one teaspoon and can decide for yourself where to round.

Spoons back out of a millilitre label

The swap button turns the page into mL → tsp, which is the direction you need when a bottle is mL-only and the instruction you were given is in spoonfuls.

Smaller steps for droppers

Searchable dropdowns on both sides reach down to microlitres, useful when an infant preparation is described in fractions of a millilitre.

One tap to a shareable number

Copy gives the plain value with no unit attached, ready to drop into a message, a medicine diary or a school medication form.

Questions About Spoons on a Medicine Label

Is a teaspoon really 5 mL, or is that a simplification?

It is a deliberate simplification. The US customary teaspoon is legally 4.92892159375 mL — a sixth of a fluid ounce — but every dosing device is manufactured to a round 5 mL. The difference is 0.071 mL on a single spoonful, about 1.4 %, which is well inside the tolerance of the device itself. Metric countries define the teaspoon as 5 mL outright, so the two systems agree in practice.

How much does a spoon from the cutlery drawer actually hold?

Anywhere from roughly 3 to 7 mL for an ordinary teaspoon, with measurements as low as about 1.5 mL and as high as 9 mL reported across household cutlery. Nothing standardises them — they are designed for stirring tea, not for measuring. At the extremes, the same "one teaspoonful" instruction could deliver under a third of the intended amount or nearly double it, and the person doing the pouring has no way of telling which spoon they are holding.

Is an oral syringe better than the little cup that comes with the bottle?

Consistently, yes. In testing by the US National Institutes of Health, syringes measured a 2.5 mL amount correctly about 94 % of the time, dosing cups about 76 %, and household spoons about 62 %. Cups suffer because the liquid is read at eye level against a curved wall and small volumes sit in the narrow taper at the bottom, where a millimetre of height is a large fraction of the amount. Syringes are drawn to a straight scale and are far easier to read at small volumes.

What is half a teaspoon in millilitres?

2.464 mL exactly, which every device rounds to the 2.5 mL mark. That marking is the smallest one on most dosing cups, and it is also where errors cluster: studies of parents measuring children's medicine found more mistakes at half-teaspoon and one-and-a-half-teaspoon amounts than at whole spoonfuls, because those are the ones people improvise. If an instruction is written in halves, an oral syringe with a 2.5 mL line removes the guesswork.

Why have labels and pharmacies moved to millilitres only?

Because the word invites the wrong tool. Regulators and safety organisations — the FDA, the ISMP and the Joint Commission among them — now recommend that oral liquid amounts be written in mL alone, with a matching device supplied. The evidence behind that is blunt: when the word "teaspoon" appeared on the label, parents were several times more likely to measure with a kitchen spoon. Removing the word removes the invitation.