Conversion from Milliliters per second to Liters per second

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 Liter per second (L/s)

The litre per second is a unit of volumetric flow rate equal to one litre passing a point every second. Its symbol is L/s. It is the unit of pumps, drains and ventilation — the scale at which a flow is large enough to be a design problem but small enough to belong to a single building.

A litre per second is a substantial stream. A kitchen tap fully open delivers about a fifth of it, a bath fills at roughly a third, and a fire hose runs at ten to twenty times as much. In visual terms it is a jet about as thick as a thumb moving briskly, and it would fill a domestic bath in about two minutes.

Building services are specified in this unit throughout Europe. Ventilation rates are given as litres per second per person — around eight to ten in an office, more in a room where people cook or exercise — and a designer multiplies that figure by the number of occupants to size the fans and the ductwork. The same unit describes rainwater drainage, where a roof's area and the local rainfall intensity together determine the flow a downpipe must carry.

Pumps are rated the same way. A domestic circulating pump moves a fraction of a litre per second, a borehole pump a few, and a large sewage pump hundreds. Because the power a pump needs is the flow multiplied by the pressure it must overcome, this figure sits at the centre of every pump calculation.

For gases the unit describes compressors and blowers, though there the volume depends on pressure and temperature and so must be stated at defined conditions. A compressor rated at fifty litres per second of free air is measured with the air at atmospheric pressure, and the same machine moving compressed air is shifting a far smaller volume.

A litre per second is a thousandth of a cubic metre per second, which is why hydrologists and building engineers rarely use the same unit even when they are describing the same water. A river carrying a cubic metre per second is carrying a thousand litres per second, and both figures are correct.

One litre per second equals 1,000 millilitres per second, 60 litres per minute, or about 0.0353 cubic feet per second.