6.5ml is equivalent to 1.32 US teaspoons.
Quickly convert Milliliters to Teaspoons (mL to tsp) at Metric-conversions.org.
Milliliter is a metric unit of volume equal to one thousandth (0.001) of a liter. Teaspoons have several different kinds of measurement available - US, UK and Metric.
US tsp = mL * 0.20288
UK tsp = mL * 0.28156
Metric tsp = mL * 0.20000
You can also check Metric Conversions if you need to convert more.
The metric system originated in France in 1799 following the French Revolution although decimal units had been used in many other countries and cultures. There have been many different measurements and the definitions of the units have been revised and the official system of measurements of most countries is the modern form of the metric system which is known as the "International System of Units".