The millilitre per hour is a unit of volumetric flow rate equal to one millilitre passing a point every hour. Its symbol is mL/h. It is the unit of slow, sustained delivery, and above all of the infusion pumps that keep hospital patients supplied with fluid, nutrition and medication over many hours.
An intravenous line is almost always programmed in millilitres per hour. Maintenance fluid for an adult runs at 80 to 125, a slow drug infusion at 5 to 20, and a paediatric or neonatal line at 1 or 2. Those are the numbers a nurse enters, and the pump converts them into the mechanical rate of a screw driving a syringe plunger.
At the bottom of that range the precision required is remarkable. A syringe driver set to one millilitre per hour is advancing the plunger by a fraction of a millimetre per minute, and it must do so smoothly enough that the drug arrives at a steady concentration rather than in pulses. The engineering of these devices is largely about eliminating the stiction that would otherwise make the delivery uneven.
Insulin pumps work below this again, in tenths of a millilitre per hour, and deliver in tiny discrete pulses rather than continuously. Implanted pumps for pain medication may run at a fraction of a millilitre per day, which is a thousandth of a millilitre per hour, and are refilled at intervals of months.
Outside medicine the unit describes laboratory perfusion, slow chemical dosing, and the leakage rates that a seal is designed to stay below. A seal specified to leak less than a millilitre per hour is losing about a cupful a week, which for many purposes is entirely acceptable and for others is a failure.
For scale, a millilitre per hour would take a full day to fill a tablespoon and about a month to fill a small cup. It is slow enough that the total delivered over a shift is the meaningful quantity, and every pump displays that alongside the rate.
One millilitre per hour equals about 0.01667 millilitres per minute, 0.000278 millilitres per second, or 0.001 litres per hour.
| Unit | Symbol | 1 Milliliter per hour equals | 1 of these equals | Converter |
|---|---|---|---|---|
| Milliliter per second | mL/s | 0.000277777777778 mL/s | 3600 mL/h | Milliliters per hour to Milliliters per second |
| Milliliter per minute | mL/min | 0.0166666666667 mL/min | 60 mL/h | Milliliters per hour to Milliliters per minute |
| Liter per second | L/s | 0.000000277777777778 L/s | 3600000 mL/h | Milliliters per hour to Liters per second |
| Liter per minute | L/min | 0.0000166666666667 L/min | 60000 mL/h | Milliliters per hour to Liters per minute |
| Liter per hour | L/hour | 0.001 L/hour | 1000 mL/h | Milliliters per hour to Liters per hour |
| Cubic millimeter per second | mm³/s | 0.277777777778 mm³/s | 3.6 mL/h | Milliliters per hour to Cubic millimeters per second |
| Cubic millimeter per minute | mm³/min | 16.6666666667 mm³/min | 0.06 mL/h | Milliliters per hour to Cubic millimeters per minute |
| Cubic millimeter per hour | mm³/hour | 1000 mm³/hour | 0.001 mL/h | Milliliters per hour to Cubic millimeters per hour |
| Cubic centimeter per second | cm³/s | 0.000277777777778 cm³/s | 3600 mL/h | Milliliters per hour to Cubic centimeters per second |
| Cubic centimeter per minute | cm³/min | 0.0166666666667 cm³/min | 60 mL/h | Milliliters per hour to Cubic centimeters per minute |
| Cubic centimeter per hour | cm³/h | 1 cm³/h | 1 mL/h | Milliliters per hour to Cubic centimeters per hour |
| Cubic meter per second | m³/s | 2.77777777778 × 10-10 m³/s | 3600000000 mL/h | Milliliters per hour to Cubic meters per second |
| Cubic meter per minute | m³/min | 0.0000000166666666667 m³/min | 60000000 mL/h | Milliliters per hour to Cubic meters per minute |
| Cubic meter per hour | m³/h | 0.000001 m³/h | 1000000 mL/h | Milliliters per hour to Cubic meters per hour |
| Cubic inch per second | in³/s | 0.0000169510400263 in³/s | 58993.4304 mL/h | Milliliters per hour to Cubic inches per second |
| Cubic inch per minute | in³/min | 0.00101706240158 in³/min | 983.22384 mL/h | Milliliters per hour to Cubic inches per minute |
| Cubic inch per hour | in³/h | 0.0610237440947 in³/h | 16.387064 mL/h | Milliliters per hour to Cubic inches per hour |
| Cubic foot per second | ft³/s | 0.00000000980962964555 ft³/s | 101940647.724 mL/h | Milliliters per hour to Cubic feet per second |
| Cubic foot per minute | ft³/min | 0.000000588577778733 ft³/min | 1699010.7954 mL/h | Milliliters per hour to Cubic feet per minute |
| Cubic foot per hour | ft³/h | 0.000035314666724 ft³/h | 28316.84659 mL/h | Milliliters per hour to Cubic feet per hour |
| Fluid ounce per second | fl oz/s | 0.00000977641103552 fl oz/s | 102287.025 mL/h | Milliliters per hour to Fluid ounces per second |
| Fluid ounce per minute | fl oz/min | 0.000586584662131 fl oz/min | 1704.78375 mL/h | Milliliters per hour to Fluid ounces per minute |
| Fluid ounce per hour | fl oz/h | 0.0351950797279 fl oz/h | 28.4130625 mL/h | Milliliters per hour to Fluid ounces per hour |
| Gallon per second | gal/s | 0.000000061102568972 gal/s | 16365924 mL/h | Milliliters per hour to Gallons per second |
| Gallon per minute | gal/min | 0.00000366615413832 gal/min | 272765.4 mL/h | Milliliters per hour to Gallons per minute |
| Gallon per hour | gal/h | 0.000219969248299 gal/h | 4546.09 mL/h | Milliliters per hour to Gallons per hour |
| US Gallon per second | gal US/s | 0.000000073381125655 gal US/s | 13627482.4224 mL/h | Milliliters per hour to US Gallons per second |
| US Gallon per minute | gal US/min | 0.0000044028675393 gal US/min | 227124.70704 mL/h | Milliliters per hour to US Gallons per minute |
| US Gallon per hour | gal US/h | 0.000264172052358 gal US/h | 3785.411784 mL/h | Milliliters per hour to US Gallons per hour |