Teaspoons to Milliliters Converter
Convert US teaspoons to milliliters — and why a medicine spoon is 5 mL, not 4.93.
Updated
milliliters
4.93mL
1 tsp = 4.93 mL
In short
How many mL is a teaspoon?
One US teaspoon is 4.93 millilitres, from the exact figure 4.92892159375. The metric teaspoon used in most of the world is a round 5 mL, so the two differ by 1.44 percent and can be swapped in cooking without consequence. For medicine, use the marked syringe or cup that came with the bottle rather than either spoon.
A teaspoon on a medicine label means 5 mL by pharmaceutical convention, not the 4.93 mL customary teaspoon.
US teaspoons to milliliters — quick reference
| US teaspoons (tsp) | milliliters (mL) |
|---|---|
| 0.1 tsp | 0.62 mL |
| 0.3 tsp | 1.23 mL |
| 0.5 tsp | 2.46 mL |
| 0.8 tsp | 3.70 mL |
| 1 tsp | 4.93 mL |
| 1.5 tsp | 7.39 mL |
| 2 tsp | 9.86 mL |
| 3 tsp | 14.79 mL |
The formula, worked line by line
The conversion is a multiplication by a constant that was defined rather than measured. The US teaspoon is one sixth of the US fluid ounce, the fluid ounce is one hundred and twenty-eighth of the US liquid gallon, and the gallon is exactly 231 cubic inches. Fix the inch at 2.54 centimetres and every figure downstream becomes exact.
“The US gallon is exactly 231 cubic inches, and the inch is exactly 2.54 centimetres.”
Because each step is exact, the conversion contributes no error whatsoever. Whatever inaccuracy ends up in the pan or the dosing cup comes from the spoon, the fill and the pour, which is the reason this page spends more words on the device than on the arithmetic.
mL = US tsp x 4.92892159375
4.92892159375 = 29.5735295625 / 6 (the fluid ounce, split six ways)
1 tsp -> 1 x 4.92892159375 = 4.93 mL
3 tsp = 1 tbsp - 6 tsp = 1 fl oz - 48 tsp = 1 cup
metric spoon: mL = spoons x 5- Teaspoons entered
- 1
- Exact factor
- 4.92892159375 mL per teaspoon
- Multiplication
- 1 x 4.92892159375 = 4.92892159375
- Millilitres
- 4.93 mL
Against the metric 5 mL spoon that is a shortfall of 0.07 millilitres, or 1.44 percent. To put that in perspective, it is about one and a half drops. No kitchen spoon can be filled to that tolerance twice in a row, which is why the two units are treated as interchangeable everywhere except a pharmacy.
What 1.44 percent costs when you scale it
The error is proportional and always runs the same way, so it accumulates rather than cancelling. At one teaspoon it is invisible. At a full cup measured out in teaspoons it reaches about 3.4 millilitres, which is a little over two thirds of one spoon. That is the point where the choice of spoon starts to be a real decision.
- At 1 tsp
- 0.07 mL over, invisible
- At 3 tsp, one tablespoon
- 0.21 mL over
- At 12 tsp, a quarter cup
- 0.85 mL over
- At 48 tsp, one cup
- 3.41 mL over
Nobody measures a cup in teaspoons, which is precisely why the substitution is safe in practice — the quantities where the error would matter are the ones measured with a different tool.
The Australian tablespoon changes the ladder
Three teaspoons make a tablespoon in the US, the UK and most of the world. Australia is the exception: its tablespoon is 20 millilitres, which is four metric teaspoons rather than three. A recipe of Australian origin calling for a tablespoon means a third more than an American one, and that gap is large enough to change a batter or a sauce.
How to use the teaspoons to milliliters converter
One US teaspoon is 4.92892159375 millilitres, which displays as 4.93. The figure comes straight out of the fluid ounce: a teaspoon is a sixth of one, a tablespoon is half of one, and the fluid ounce itself is the US gallon divided by 128. Nothing along that chain is measured, so the awkward decimal terminates rather than repeating.
For cooking, the number you actually need is 5. The metric teaspoon sold everywhere outside the United States is a round 5 millilitres, which is 1.44 percent larger than the US one. On a single teaspoon that is seven hundredths of a millilitre, a quantity no spoon can express and no palate can detect.
4.93 mL
One US teaspoon
exactly 4.92892159375
5 mL
The metric teaspoon
1.44 percent larger
2.5 to 7.3 mL
Measured household teaspoons
Falagas et al., 2010
The third figure is the one worth stopping on. When researchers actually measured the capacity of 71 household teaspoons, they held between 2.5 and 7.3 millilitres, averaging 4.4. The spoon in a cutlery drawer is not a teaspoon in any defined sense, and the gap between 4.93 and 5.00 is trivial beside it.
For recipes, the practical rule is that teaspoons and millilitres are interchangeable at small quantities and stop being so when scaled. A single teaspoon converted at 5 rather than 4.93 is 1.44 percent high. The same rounding applied across twenty-four teaspoons of liquid in a batch adds about 1.7 millilitres, which is still nothing.
- 0.25 tsp, a quarter teaspoon
- 1.23 mL
- 0.5 tsp, a half teaspoon
- 2.46 mL
- 1 tsp
- 4.93 mL
- 3 tsp, one tablespoon
- 14.79 mL
- 6 tsp, one fluid ounce
- 29.57 mL
- 48 tsp, one cup
- 236.59 mL
Three teaspoons to the tablespoon and six to the fluid ounce are exact ratios, so every rung follows from the one above without a second lookup.
When the recipe gives fluid ounces instead
Six teaspoons make one fluid ounce. If the quantity you are holding is written in ounces rather than spoons, that page multiplies by the exact 29.5735295625 millilitre fluid ounce.
Open the fluid ounce converter →US teaspoons converted to millilitres, with the equivalent in metric 5 mL spoons alongside. The third column shows how little the difference between the two systems amounts to at kitchen quantities.
| US teaspoons | Millilitres | In metric 5 mL spoons |
|---|---|---|
| 0.25 tsp | 1.23 mL | a quarter spoon |
| 0.5 tsp | 2.46 mL | a half spoon |
| 0.75 tsp | 3.70 mL | three quarters |
| 1 tsp | 4.93 mL | 0.99 spoons |
| 1.5 tsp | 7.39 mL | 1.48 spoons |
| 2 tsp | 9.86 mL | 1.97 spoons |
| 3 tsp | 14.79 mL | one tablespoon |
| 4 tsp | 19.72 mL | 3.94 spoons |
| 6 tsp | 29.57 mL | one fluid ounce |
| 8 tsp | 39.43 mL | 7.89 spoons |
| 12 tsp | 59.15 mL | a quarter cup |
| 16 tsp | 78.86 mL | 15.77 spoons |
| 24 tsp | 118.29 mL | half a cup |
The teaspoon on a medicine label is 5 mL
Pharmaceutical practice settled this a long time ago. Where a medicine label says a teaspoon, the intended quantity is 5 millilitres rather than the 4.93 millilitre customary teaspoon, and any dropper, cup or spoon calibrated with a teaspoon mark is meant to deliver 5 millilitres at that mark. Approved labelling routinely spells it out as one teaspoon, 5 mL.
That convention removes the definitional ambiguity but not the hazard, because the hazard was never definitional. The Institute for Safe Medication Practices lists both tsp and tbsp among its error-prone abbreviations, noting each can be mistaken for the other, and gives millilitres as the best practice for prescribing, dispensing and administration alike.
- A metal kitchen teaspoon
- mean fell between 3.90 and 4.08 mL
- A calibrated medicine spoon
- mean fell between 4.91 and 5.09 mL
- An oral syringe
- mean fell between 5.09 and 5.17 mL
- Spread, metal spoon against syringe
- standard deviation 0.749 against 0.348 mL
- The device, not the unit
- is what decides the dose
From Beckett and colleagues in Archives of Disease in Childhood, 2012. The kitchen spoon did not merely read low, it read inconsistently: its spread was more than twice the syringe. A dose that is sometimes right and sometimes twenty percent out is the actual failure mode.
The paediatric guidance follows from that evidence rather than from unit pedantry. The Academy asks for millilitres when prescribing and administering, for mL as the only abbreviation used, and for an appropriately sized millilitre-marked device supplied with the medicine, preferably an oral syringe rather than any kind of spoon.
Why the decimal is so ugly
A teaspoon looks like it should be a round number and is not, because it was never defined against the millilitre. It was defined against the US gallon, which was defined as 231 cubic inches, which became exact in litres only in 1959 when the inch was fixed at 2.54 centimetres. Everything downstream inherited that chain.
Divide the gallon by 128 for the fluid ounce and by six again for the teaspoon and you get 4.92892159375 millilitres. The digits terminate, which tells you the definition is exact rather than approximate. A repeating decimal would have meant a measured relationship; a terminating one means the two units are locked together by definition.
- US liquid gallon
- 231 cubic inches, exactly
- In litres, once the inch is 2.54 cm
- 3.785411784 L
- Divided by 128, the fluid ounce
- 29.5735295625 mL
- Divided by 6, the teaspoon
- 4.92892159375 mL
The metric teaspoon of 5 mL was chosen for convenience rather than derived, which is exactly why it is round.
This is also why the two systems will never converge. The metric spoon was picked to be a tidy number of millilitres, and the customary one fell out of a gallon defined in cubic inches two centuries earlier. They land 1.44 percent apart by accident, close enough that nobody had to choose between them in a kitchen.
Every US teaspoons value, worked out
29 common US teaspoons figures each get their own page, with the answer at full precision, the arithmetic, what rounding costs, and the nearest real-world reference point on the scale.
Questions people ask
Sources
Where the constants and formulas on this page come from. Each line names the figure it backs.
The US teaspoon is one sixth of the US fluid ounce of exactly 29.5735295625 millilitres, giving 4.92892159375 mL.
NIST Guide to the SI, Appendix B.8 — Factors for units listed alphabetically — NIST
Measured capacities of 71 household teaspoons ranged from 2.5 to 7.3 mL with a mean of 4.4 mL, and 49 tablespoons from 6.7 to 13.4 mL.
Inaccuracies in dosing drugs with teaspoons and tablespoons — International Journal of Clinical Practice, 2010
Of 277 caregivers aiming at a 5 mL dose, the metal teaspoon group averaged between 3.90 and 4.08 mL with more than double the spread of an oral syringe.
Accurately administering oral medication to children isn't child's play — Archives of Disease in Childhood, 2012
Millilitres alone are recommended for prescribing and administering oral liquid medicines, with teaspoon and tablespoon dosing avoided and an mL-marked device supplied.
Metric Units and the Preferred Dosing of Orally Administered Liquid Medications — American Academy of Pediatrics, 2015, reaffirmed 2025
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