Article — mL to Teaspoons Converter
mL to teaspoons: four definitions of "1 tsp" and why the FDA stopped using the word
- How many millilitres are in a teaspoon?
- The four teaspoon standards in use today
- The Australian tablespoon: a 33% outlier
- Why the FDA pushed labels from tsp to mL
- Common 5, 10, 15 and 30 mL conversions
- The 2-to-9 mL kitchen spoon problem
- Cooking precision and when teaspoons stop working
- Which teaspoon does your context use?
A metric teaspoon is 5 millilitres exactly. The US customary teaspoon is 4.92892 mL. The imperial UK teaspoon is 5.919 mL. The Australian teaspoon is the metric 5 mL - but the Australian tablespoon is 20 mL, not 15. The calculator above runs the conversion in both directions for all four standards. For medication dosing, the FDA, AAP, and CDC all recommend ignoring the word "teaspoon" entirely and using a calibrated oral syringe with mL markings.
For most cooking, 1 tsp = 5 mL is correct everywhere. The 1.4% gap between the US customary teaspoon and the metric teaspoon is too small to matter for soups, sauces, or seasonings. Baking is a different story - the metric teaspoon is the standard for any recipe that needs to scale cleanly.
How many millilitres are in a teaspoon?
The answer depends on which teaspoon and which context. Four definitions exist in active use, with a 20% spread from smallest to largest. Modern global usage has consolidated around the metric value, but recipes and labels from earlier eras specify other standards.
- US customary tsp = 4.92892 mL (older American recipes, pre-2011 US drug labels)
- Metric tsp = 5 mL exactly (international standard, modern pharmacy, EU recipes)
- Australian tsp = 5 mL (metric value, but 4 tsp per tbsp instead of 3)
- Imperial UK tsp = 5.919 mL (pre-1970s British recipes, defined as 1/3 of an imperial tablespoon (1/24 imperial gill))
- Drawer teaspoon = 2 to 9 mL (measured range across actual household spoons)
NIST's Metric Kitchen reference table uses 4.92892 mL for the US customary teaspoon, derived from 1/6 of a US fluid ounce (29.5735 mL / 6 = 4.92892 mL). For most cooking purposes, the difference between this value and the round 5 mL of the metric teaspoon does not affect the result. For pharmaceutical and pediatric work, both values are considered equivalent for dosing - the actual concern is the variability of household spoons, not the formal definition.
The four teaspoon standards in use today
The history is the same story as cups and tablespoons: pre-metric national customs were absorbed into the metric system at different times, leaving behind different starting points. The teaspoon was the smallest of the customary apothecary units, and it survived the metrication of every country that adopted it.
The Australian tablespoon: a 33% outlier
Australia adopted the metric system in the 1970s and standardised the teaspoon at 5 mL, the same as everyone else. The tablespoon went a different direction. When Australia rewrote its cooking conventions for metric, the new official tablespoon was fixed at 20 mL - four teaspoons - rather than the 15 mL (three teaspoons) used in the US, UK, NZ, Canada, and most of Europe. The reason was local: many Australian recipes had been written for a "dessertspoon" of roughly 20 mL, and the government chose to keep that volume under the new tablespoon name.
An Australian recipe that calls for "1 tablespoon of olive oil" wants 20 mL. The same recipe written for an American or British kitchen would call for "1 tablespoon," meaning 15 mL. The 5 mL gap per tablespoon - one entire metric teaspoon - is enough to throw off the seasoning of a dressing or the thickness of a sauce. Australian cookbooks generally specify "Australian tablespoons" when the recipe is for export.
The Australian teaspoon, by contrast, is the same 5 mL as everywhere else, so the rule "1 tbsp = 3 tsp" fails only in Australia. Australian recipes use the relation 1 tbsp = 4 tsp = 20 mL. For mL-to-teaspoon conversions, the calculator output is identical for Australian and metric standards; the difference appears only when tablespoons enter the picture.
Why the FDA pushed labels from tsp to mL
In 2011, the American Academy of Pediatrics and the FDA published guidance recommending that liquid medication be labelled and dosed in millilitres only. The trigger was a series of pediatric dosing errors: parents were measuring children's medication with whatever spoon was at hand, and the resulting doses varied by a factor of three or more.
A study published in the journal Pediatrics in 2014 found that parents who used kitchen spoons made dosing errors at over thirty times the rate of parents using a calibrated oral syringe with mL markings. After the FDA's 2016 labelling change to mL-only on OTC liquid medications - implemented by Tylenol, Motrin, and other manufacturers - the rate of kitchen-spoon dosing dropped from 31.3% to 15.4% of parents, according to the CDC PROTECT Initiative. The labelling change cut spoon-dosing errors approximately in half.
A teaspoon pulled from a drawer ranges from 2 to 9 mL of usable volume - up to 4x off from the standard 5 mL. Mistaking a tablespoon for a teaspoon is a triple dose. The American Academy of Pediatrics, the FDA, and the CDC all recommend using the calibrated oral syringe that ships with childrens medication, marked in millilitres. This calculator is for cooking and reference, not for medication.
Common 5, 10, 15 and 30 mL conversions
The most-searched volumes and their teaspoon equivalents in the three main standards:
1.25 mL 0.25 metric tsp (¼ tsp)2.5 mL 0.50 metric tsp (½ tsp)5 mL 1.00 metric tsp / 1.01 US tsp10 mL 2.00 metric tsp / 2.03 US tsp15 mL 3.00 metric tsp = 1 tbsp (US/UK)20 mL 4.00 metric tsp = 1 Australian tbsp30 mL 6.00 metric tsp = 2 tbsp50 mL 10.00 metric tsp = ~3⅓ tbspThe 2-to-9 mL kitchen spoon problem
Measurement studies of household teaspoons have repeatedly found wide volume variation. A 2010 study at the University of Iowa tested a set of household teaspoons and found volumes ranging from 2.5 mL to 7.3 mL across a single kitchen drawer. Industrial flatware studies have measured drawer teaspoons as small as 2 mL and as large as 9 mL. The "teaspoon" label on cutlery refers to the spoon's purpose, not a defined volume.
Measuring spoons, which are dedicated kitchen tools sold in nested sets, are far closer to standard. A measuring teaspoon labelled "1 tsp" typically holds 5 mL with a tolerance of about 5%. The accuracy is adequate for cooking but still not appropriate for medication: an oral syringe is graduated to 0.1 mL and removes the level-versus-rounded question entirely.
For cooking, a nested set of measuring spoons (1 tsp, ½ tsp, ¼ tsp, plus a 1 tbsp) costs $4 to $8 and lasts forever. Use these for any recipe where the seasoning balance matters - especially salt, baking soda, and yeast. For medication, the dosing tool included with the medication is the right tool, every time, without exception.
Cooking precision and when teaspoons stop working
For soups, sauces, marinades, and most savoury cooking, teaspoon precision is adequate - a teaspoon more or less of vinegar, soy sauce, or hot sauce changes the dish only slightly. For baking, teaspoons are accurate enough for leaveners (baking soda, baking powder), salt, and spices, all of which are used in small enough quantities that the volume-versus-weight gap is small.
The teaspoon stops working as a unit when the recipe needs many of them. A bread recipe specifying "20 tsp of water" is silly - that is 100 mL, which is easy to measure directly. Professional and modern home recipes have largely moved to mL for liquids and grams for dry ingredients, reserving teaspoons for items where the quantity genuinely is one to three teaspoons. King Arthur Baking, America's Test Kitchen, and modern cookbook authors now write metric primary, US customary secondary.
Which teaspoon does your context use?
For modern recipes from anywhere, use the metric teaspoon (5 mL) - this is the default in the European Union, Australia, New Zealand, Canada, and increasingly the United States. For older American recipes that specify customary units, use the US customary teaspoon (4.929 mL) - the difference is rarely noticeable. For older British recipes published before the 1970s metric transition, use the imperial UK teaspoon (5.919 mL). For Australian recipes, use the metric teaspoon but remember the 20 mL Australian tablespoon. For medication, do not use any teaspoon at all - use the calibrated dosing tool that comes with the medication, marked in mL.