Is 1 tsp Equal to 5ml? A Complete Kitchen Guide

November 30, 2025 •

4 min read

According to the National Institute of Standards and Technology (NIST), a United States customary teaspoon is precisely 4.92892159375 milliliters, which is why 1 tsp is commonly equated to 5ml for practical purposes. This rounding makes it easy for everyday use, but the small difference can be important in certain applications, such as pharmaceutical dosing or chemistry experiments. Understanding this nuance is key to achieving accuracy in your kitchen and for health-related measurements.

Quick Summary

This guide explains why 1 teaspoon is generally considered equal to 5ml, examining the standards for metric vs. US customary teaspoons. It also covers the critical differences between a standard measuring spoon and a household spoon for both culinary accuracy and safe medication administration.

Key Points

Standard Conversion: For everyday cooking and metric applications, 1 tsp is standardized and widely accepted as 5ml.
Household Spoon Inaccuracy: Never use a regular cutlery teaspoon for measuring, especially for medicine, as its volume can vary significantly.
US vs. Metric: While the US customary tsp is technically 4.93ml, it is rounded to 5ml for practical use, aligning it with the metric standard.
Safety First: For medication, use a purpose-built oral syringe or medicine cup with clear milliliter markings to ensure safe and accurate dosing.
Baking Precision: Accuracy is critical in baking; using standardized measuring spoons prevents recipe failures from incorrect leavening or ingredient ratios.

Standardizing Teaspoon Measurements

In the world of cooking, baking, and medicine, precise measurements are crucial. The question of "Is 1 tsp equal to 5ml?" has a nuanced but clear answer based on international and national standards. For metric measurements, and in much of the world, a standard teaspoon is formally defined as exactly 5ml. In the United States, the customary teaspoon is defined slightly differently but is rounded up to 5ml for all practical cooking and nutritional labeling purposes. This metrication simplifies conversions and ensures consistency in modern recipes and pharmaceutical instructions worldwide. Therefore, when following a recipe from a cookbook published in a metric country, or when measuring liquid medicine, you can reliably assume that 1 teaspoon equals 5ml.

The Peril of Household Spoons

The most significant factor in this conversion is using the right tool. Studies have repeatedly shown that a regular teaspoon found in your silverware drawer is not a reliable measuring device. The volume of household teaspoons can vary dramatically, holding anywhere from 2.5ml to over 7ml. This inconsistency can lead to improper results in cooking and, more dangerously, incorrect medication dosages. For this reason, healthcare professionals strongly advise against using everyday cutlery for administering medicine. Always use a standardized measuring spoon set, a medicine cup, or an oral syringe for the most accurate results.

US Customary vs. Metric Teaspoons

While the rounded figure of 5ml is used almost universally, there is a slight technical difference between the US customary and metric teaspoons. This discrepancy is typically insignificant for everyday culinary tasks but becomes relevant when extreme precision is necessary.

US Customary Teaspoon: Defined as 1/6th of a US fluid ounce, which is precisely 4.92892159375 milliliters.
Metric Teaspoon: Standardized globally as exactly 5 milliliters.

This minimal 0.07ml difference is negligible for home cooks but emphasizes why professional bakers or scientists might use different equipment. It's a key detail for understanding the complete picture of the measurement standard. For home cooks, using a metric measuring spoon set, where 1 tsp is labeled as 5ml, is the best way to maintain consistency with modern recipes.

List of Common Teaspoon Conversions

For quick reference, here are some common conversions based on the 1 tsp = 5ml standard:

1/4 tsp = 1.25 ml
1/2 tsp = 2.5 ml
1 tsp = 5 ml
2 tsp = 10 ml
3 tsp (1 Tbsp) = 15 ml
4 tsp = 20 ml

The Role of Accuracy in Baking and Medicine

Precision in measurement is not just a matter of following instructions—it's a critical component of safety and success. In baking, minor deviations can dramatically affect the chemical reactions that determine a recipe's outcome. Too much or too little leavening agent, for example, can cause a cake to fall flat or become overly dense. Similarly, in medicine, the stakes are much higher. A 2017 study cited by Harvard Health reported that variations in household spoon sizes contributed to incorrect medication dosages, highlighting the health risks involved. Always prioritize accuracy when health and safety are on the line. For liquid medicine, utilize the measuring tool provided with the medication.

Comparison of Measurement Devices

Understanding the differences between common kitchen measuring tools is vital for getting your measurements right. Not all tools are created equal, and choosing the correct one for the task at hand can make a world of difference.


Feature	Standard Measuring Spoon	Oral Medication Syringe	Household Cutlery Spoon
Accuracy	High. Designed to hold a specific, standardized volume.	Highest. Marked with precise millimeter graduations for exact dosing.	Highly Variable. Volume is not standardized and can vary widely.
Best for	Cooking and baking recipes that specify tsp measurements.	Administering liquid medications, especially for small doses.	Not recommended for measuring; suitable for serving or eating.
Clarity	Clear markings (1/4 tsp, 1/2 tsp, 1 tsp, etc.).	Clear markings in milliliters (ml) and sometimes teaspoons.	No standardized markings; rely on rough visual estimates.
Safety	Very safe for culinary use.	Essential for ensuring correct medical dosing.	Unsafe for medication dosing due to high variability.

Conclusion: Precision Over Approximation

The simple answer to "is 1 tsp equal to 5ml?" is yes, for all practical intents and purposes. This standard conversion is widely accepted in cooking and for metric applications. However, this approximation holds true only when using a standardized, level measuring spoon. For critical applications, such as administering medicine, it is imperative to use a tool with precise millimeter markings to ensure safety and accuracy. For the home cook, investing in a good set of measuring spoons eliminates the guesswork and helps guarantee consistent and delicious results. Ultimately, understanding the difference between the standard conversion and the pitfalls of imprecise household tools is key to mastering measurement in both the kitchen and the medicine cabinet.

Frequently Asked Questions

Yes, technically there is a very slight difference. A US customary teaspoon is precisely 4.92892159375 milliliters, while a metric teaspoon is exactly 5 milliliters. For all practical purposes in cooking and baking, this difference is negligible, and they are treated as equal.

Household teaspoons vary widely in size and are not standardized for volume. This inconsistency means you could accidentally give an incorrect dose of medication, which can be dangerous. Always use a proper measuring tool like an oral syringe or a dedicated medicine cup for accuracy.

Using the standard conversion, a half teaspoon (1/2 tsp) is equal to 2.5 milliliters.

In countries that use the metric system, a teaspoon is defined as 5ml. For countries using US customary measurements, the standard culinary and nutritional labeling teaspoon is rounded to 5ml for simplicity, so the conversion is widely consistent across modern usage.

For the highest level of accuracy, especially for medication, use an oral syringe or medicine cup with clear milliliter markings. For cooking and baking, a standardized measuring spoon clearly marked as 5ml or 1 tsp is sufficient.

Yes, you can use a measuring teaspoon for solid ingredients like salt or spices. For the most accurate measurement, it is best to level off the contents with a straight edge, such as the back of a knife.

Three teaspoons make one tablespoon (3 tsp = 1 tbsp). This also means that 1 tablespoon is equivalent to 15 milliliters.