Conversion from Milliliters per second to Cubic centimeters per hour

Information about the Milliliter per second (mL/s)

The millilitre per second is a unit of volumetric flow rate equal to one millilitre of fluid passing a point every second. Its symbol is mL/s. Since a millilitre is a cubic centimetre, the unit is identical to the cubic centimetre per second, and the two names are used interchangeably depending on whether the fluid is thought of as a liquid or as a volume of space.

Volumetric flow rate is a volume divided by a time, so it has the dimensions of length cubed per second. That makes it convertible to any other flow unit by a single multiplication, and it also means that a flow rate multiplied by a duration gives the total volume delivered — the arithmetic that underlies every dosing calculation and every water bill.

A millilitre per second is a small but visible flow. A tap dripping steadily produces perhaps a tenth of this; a thin stream from a partly opened tap is a few millilitres per second; a garden hose at full flow is several hundred. In household terms it is the rate at which a teaspoon fills in about five seconds.

The unit belongs to the laboratory and to small machinery. Peristaltic pumps, dosing systems, fuel injectors and analytical instruments all work in this range, and their specifications are written in millilitres per second when the process is fast and in millilitres per minute when it is slow. Where a pump must deliver a precise quantity, the rate and the running time together define the dose.

Human physiology gives useful comparisons. Resting cardiac output is about eighty millilitres per second, urine production averages under a fiftieth of that, and saliva production is around a hundredth. The flow through a single capillary is far smaller still and is measured in cubic millimetres per hour.

Converting to the SI base unit requires care with the powers of ten. One millilitre per second is a millionth of a cubic metre per second, because a millilitre is a millionth of a cubic metre. That factor of a million between the practical unit and the base unit is why flow rates are almost never quoted in cubic metres per second outside hydrology and heavy engineering.

One millilitre per second equals 0.001 litres per second, 60 millilitres per minute, or about 0.0000353 cubic feet per second.

Information about the Cubic centimeter per hour (cm³/h)

The cubic centimetre per hour is a unit of volumetric flow rate equal to one cubic centimetre passing a point every hour. Its symbol is cm³/h, and because a cubic centimetre is a millilitre, mL/h means the same rate. It describes flows slow enough that nothing appears to move, yet fast enough to matter over a shift or a night.

Hospital infusion is its most common setting. A syringe driver or volumetric pump is programmed in millilitres per hour: maintenance fluid at 80 to 120 for an adult, a sedative at 5, a neonatal feed at less than 1. The nurse setting the pump and the pharmacist calculating the dose both work in this unit, and the dose in milligrams per hour follows from it and the concentration of the bag.

Leak testing uses the unit as a pass-or-fail criterion. A hydraulic fitting, a fuel connector or a refrigeration joint is given an allowable leakage of so many cubic centimetres per hour, measured by collecting what escapes over a long period rather than by watching for a drip. Regulations on refrigerant loss and on vehicle fuel-system emissions are written this way.

Lubrication systems are rated here as well. A centralised oil-drip system on a machine tool delivers a few cubic centimetres per hour to each bearing, and an air-line oiler set correctly gives one drop every few minutes. Too much and the oil contaminates the workpiece; too little and the bearing fails, which is why the rate is specified rather than left to judgement.

Evaporation and drying processes are quantified in the same terms. A solvent evaporating from an open dish, water lost from a laboratory culture, or condensate produced by a small dehumidifier are all naturally described per hour, because the observation period is an hour or a day rather than a second.

The relation to bigger units keeps the scale clear. A thousand cubic centimetres per hour is a litre per hour, and a full day at one cubic centimetre per hour yields 24 cubic centimetres — about a tablespoon and a half. That is the honest measure of what a slow flow accomplishes while nobody is watching.

One cubic centimetre per hour equals one millilitre per hour, about 0.01667 cubic centimetres per minute, or 0.001 litres per hour.