So exactly how many milligrams are there in a milliliter? The first step to answering this question is to understand what the letter 'm' means when applied to units. It means one-thousandth (1/1000) of the original unit. Therefore we're asking how many thousandths of a gram are there in a thousandth of a liter. Recall that a gram is one-thousandth of a kilogram. If you need help converting weight from a different unit to mg, our weight converter can help.

Now that we've sorted that out, the question is now "What is the relationship between kilograms and liters?" The kilogram was originally defined in 1795 as equal to one liter of water at the temperature of melting ice (0 °C / 32 °F). That's not entirely true in the present day, as the kilogram and meter (a liter is the volume of one-thousandths of a cubic meter) have been re-defined, but it's very close indeed (0.9998 kg is a more precise figure). A syringe is a medical device that is used to inject fluid into, or withdraw fluid from, the body. They are also used to measure the volume of fluid in a body cavity or organ. The pressure in a syringe is calculated by the force applied to the plunger divided by the cross-sectional area of the plunger. This can be done by using the equation: Where P is the pressure in Pa (pascals), F is the force in N (newtons), and A is the area in m So, a milligram is a thousandth of a thousandth of a kilogram, and a milliliter is a thousandth of a liter. Notice there is an extra thousandth on the weight unit. Therefore, there must be 1,000 milligrams in a milliliter, making the formula for mg to ml conversion: