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Units of liquid and dry capacity mainly used in cooking and to give medicines at home.
In the United States, 1 teaspoon = ¹⁄₃ of a tablespoon = 5 milliliters¹. Abbreviation, according to the U.S. FDA requirements for food labeling, “tsp”,² but in recipes often “t”. The corresponding abbreviations for the tablespoon are tbsp and "T".
Earlier, i was equal to 4.928 922 milliliters. A study several decades ago by the U.S. Bureau of Standards found that the typical silver teaspoon and measuring teaspoon held 1½ fluid drams (about 5.5 mL), not the 1 fluid dram (about 3.7 mL) often given in reference works.
In a publication of 1975 that anticipated conversion to the metric system, the National Bureau of Standards said:
There will be no need for much change in our recipes if the new metric recipes remain volumetric and if, as anticipated, the utensils retain approximately the same ratio as the customary cup (237 ml), teaspoon (4.9 ml), and tablespoon (14.7 ml) This is easily achieved by adopting a “metric cup” of 250 ml (¼ of a liter); a “metric teaspoon” of 5 ml, and a “metric tablespoon” of 15 ml.³
The 5 mL magnitude appeared in the late 20ᵗʰ century and is a rare example of the U.S. Government defining measures in modern times. In fact, by the 1990s almost all the teaspoon measures in stores were made to contain 5 mL, and tablespoons 15 mL, and many were so marked. In cooking, this difference makes no difference, because few cooks measure ingredients with an accuracy of 0.1 mL. In measuring doses of medicines, however, the variations in cooking measuring spoons can make a difference, and authorities advise that only spoons provided with the medicine be used.
1. “For purposes of nutrition labeling, 1 cup means 240 mL, 1 tablespoon means 15 mL, 1 teaspoon means 5 mL, 1 fluid ounce means 30 mL, and 1 ounce means 28 g.” (21 CFR 101.9(b)(5)(viii)).
2. “If a manufacturer elects to use abbreviations for units, the following abbreviations shall be used: tbsp for tablespoon, tsp for teaspoon, g for gram, mL for milliliter, oz for ounce, and fl oz for fluid ounce.” (21 CFR 101.9(b)(7)(iv))
3. United States. National Bureau of Standards.
Household Weights and Measures.
Special Publication 430.
Washington, DC: USGPO, 1975 (1978 reprint).
As the examples below show, by at least the middle of the 19ᵗʰ century physicians were aware that prescribing doses of medicines in teaspoons led to serious, sometimes fatal, over- and underdoses. Students of public health have studied what happens when kitchen measures are used to measuring doses of medicine, particularly over-the-counter liquids for children. the reference below contains an extensive bibliography. Current practice requires that only a single unit be named on the instructions and the measuring device, preferably "mL" (without explaining it stands for milliliters).
1
A moderate sized teaspoon ... should hold about 1 drachm.
ditto dessertspoon ... ditto 2 drachms
ditto tablespoon ... ditto ½ ounce.
W. B. Kesteven.
A Manual of the Domestic Practice of Medicine.
London: Longman, Brown, Green, and Longmans, 1856.
Page 194.
2
Coch. (cochleare), a spoonful.
Coch. magn., a table-spoonful.
Coch. parv., a tea-spoonful.
N. B. A modern tablespoon contains about five drachms; a teaspoon, one drachm; a dessertspoon, three drachms; and a wineglass, two ounces. In consequence of spoons varying so much in size, they ought not to be used as measures for the exhibition of potent medicines.
Francis Gurney Smith.
A Compendium of Domestic Medicine… 2nd ed.
Philadelphia: Lindsay and Blakiston, 1857.
3
Tablespoons and Teaspoons.
—A correspondence on a subject of great practical importance has recently been going on (says the Lancet) in the Pharmaceutical Journal. Mr. Proctor, of Newcastle-upon-Tyne, has pointed out some striking instances of the inconvenience and danger that may arise from the want of uniformity that at present obtains among medical men respecting the relative proportions of one tablespoonful and half an ounce. Modern tea and table-spoons are much larger than those employed forty or fifty years ago, so that a tablespoonful should no longer be taken as representing half an ounce, nor a teaspoonful as equivalent to one drachm. As a fact, however, there is a large number of prescribers, who, when they order half an ounce of medicine to be taken, mean by that one tablespoon fill, and vice vend, while a few medical men regard half an ounce as equal only to a modern dessert spoonful. It is clear, therefore, that something should be done to ensure a common standard of measurement; and as teaspoonfuls and tablespoonfuls will doubtless always continue to be most frequently employed for the purposes of dealing out doses of medicine, it would be well, as Mr. Martindale has suggested, to give a higher value to these measures. A tablespoonful is now really equal to between five and six drachms, and the tea-spoon is capable of holding from eighty to eighty-five drops, while the dessert spoon in present use comes up to nearly half an ounce. In ordering drugs in mixtures, and especially powerful or poisonous ones like strychnine and arsenical solutions, one tablespoonful should be looked upon as equal to six drachms, the dessert-spoonful to four drachms, and the teaspoonful to a drachm and a half. A twelve-ounce bottle would, according to this, contain eight doses of two tablespoonfuls each, an. eight-ounce bottle five similar doses, and a two-ounce bottle about eleven teaspoonful doses.
Upon the same subject Land and Water remarks : — The time-honoured custom of measuring doses of medicine by tablespoonfuls, teaspoonfuls, and drops has received a rude shake in the British Medical Journal by Dr. R. Farquharson, and by Mr. Proctor in the Pharmaceutical Journal. It is found that modern table and teaspoons are much larger than they were formerly, and that a tablespoon of the present day contains considerably more than half an ounce. So, also, the teaspoon is no longer equivalent to a drachm. The size of a drop has not, of course, altered, but a drop is seldom, if ever, exactly equivalent to a minim, although it is assumed to be so. Much depends on the fluid, and not a little on the shape of the bottle from which it is dropped. As a rule the minim is considerably more bulky than a drop, and thus, when medicine is dropped instead of being measured in a minim glass, the patient's doses are smaller than they should be. It would, without doubt, be much better if domestic dispensers of medicines would use graduated measures instead of spoons or drops for measuring the doses of their patients, but, as there is little chance of their doing so universally, the next best thing is to ascertain what the actual contents of “spoonfuls” really are. The average contents of tablespoons now in use equal from five to six drachms; the dessert-spoon holds nearly half-an ounce; and the teaspoon from eighty to eighty-five minims. Another useful measure for domestic purposes is the wine-glass, but this varies in its contents from two ounces and a-half to three ounces and a-quarter. These measures are, perhaps, sufficiently exact when ordinary medicine only is used, but when powerful and dangerous drugs are administered the only safe plan to adopt is to measure carefully into a graduated glass.
James Mason.
The Year-Book in Science and the Arts for 1876.
London: Ward, Lock, and Tyler, 1877.
Pages 162-163.
4
A tablespoon of liquid ... Half fluid ounce
A tablespoon of powder ... Two drachms
A teaspoon of liquid ... One fluid drachm
A teaspoon of powder ... About half a drachm.
A teaspoon of magnesia ... About twelve grains.
The Monthly Review of Dental Surgery, Vol. V, June 1876 to May 1877.
London: Smith, Elder and Co., 1877.
Page 400.
5
Taking into consideration the fact that there is a great variation in the size of teaspoons, and in the manner they are filled, 90 minims can easily be poured into a teaspoon which holds only 60 to its level surface; that some oldfashioned teaspoons hold nearly two fluid drams. These points were doubtless well known to our correspondent, who probably had this in mind when broaching the subject to the child's father.
The Western Druggist, vol 9, 1887.
Chicago: G. P. Engelhard and Co.
page 428.
6
Liquids.— English pint, 20 oz.; American pint,
16 oz.; 4 gills, 1 pint; 2 pints, 1 quart; 4 quarts, 1
gallon; tumbler, half pint; common wine-glass,
2 oz.; large wineglass, 4 oz.; common teacup,
7 oz.; 5 table-spoons, 4 oz.; 4 teaspoons, 1 oz.
…
Eight tablespoonfuls are a gill.
Four saltspoonfuls make a teaspoonful.
Four teaspoonfuls equal one tablespoonful.
…
Teaspoons vary in size, and the new ones
hold about twice as much as the old-fashioned
spoons of thirty years ago. A medium-sized
teaspoon contains about a dram.
The Detroit Journal Year-Book for 1890. No. 2.
Detroit: The Detroit Journal Company, 1890.
Page 27.
4 mL 1 teaspoon (tsp)
5 mL 1 teaspoon, medical
Merck Manual of Diagnosis and Therapy, 20th ed.
Kenilworth, NJ: Merck Sharp and Dohme Corp., 2018.
Page 3267.
7
The TEA-SPOON. Occasioned by Dr. HiLL's prescribing a Tea-Spoonful of every Medicine to every Patient indiscriminately.
HAPPY Tea-spoon, which can hit
Dr. Hill's unequall'd wit.
Patients young, and patients old,
Patients hot, and patients cold,
Patients tender, patients tough,
A Tea-spoon full is just enough.
If with tea you shake your frame,
Or with drams your head inflame,
Or with beef your paunch o'er-stuff,
A Tea-spoon full is just enough.
If in court, with brief in hand,
Or at bar, you trembling stand,
Take the dose, fear no rebuff,
A Tea-spoon full is just enough.
What is stranger still than all,
Be the Tea-spoon large or small,
Be it batter'd, broken, rough,
Still a Tea-spoon's just enough.
Order Drops, ye Medic Dunces,
Order Scruples, Drams, and Ounces,
Hill asserts, and stands it bluff,
That a Tea-spoon's just enough.
Happy Tea-spoon, thus to hit
Dr. Hill's unequall'd wit!
The Annual Register: or, a View of the History, Politicks, and Literature for the YEAR 1769. A New Edition Corrected.
London: J. Dodsley, 1779.
Pages 481-482.
In Great Britain, a teaspoon is ¼ of a tablespoon, but a spoonful of a dry ingredient traditionally means a rounded spoonful, with as much heaped above the spoon edge as lies within it. (A rounded spoonful is not a heaping spoonful, which would be as much as the spoon could hold.) On this theory, a British teaspoonful of a dry ingredient would be about 7 milliliters, or a bit short of 1½ U.S. teaspoons.
An English pharmacopeia of 1618 defined the tablespoon as the volume of distilled water weighing 3 drachms, which would be about 12 milliliters. Pharmacists, and following them such respected sources as The Economist, say the British tablespoon = half of an imperial fluid ounce, or about 14.21 milliliters, so that there would be 10 tablespoons in an imperial gill and 20 in a half pint, and the teaspoon would be about 3.55 milliliters.
Cooks, however, don't seem to agree. Mrs. Beeton, author of the classic 19th-century English cookbook, says under the heading “Liquid Measure” that a quarter pint contains “6 large tablespoonfuls.” Since an imperial quarter pint (a gill) contains 5 imperial fluid ounces, that would make the “large tablespoonful” ⁵⁄₆ of an imperial fluid ounce, about 23.7 milliliters, and the teaspoon about 6 milliliters.
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Last revised: 31 January 2020.