| Fluid ounces per hour (fl oz/h) | Cubic feet per hour (ft³/h) |
|---|---|
| 1 Fluid ounce per hour | 0.0010033978328 ft³/h |
| 2 Fluid ounces per hour | 0.00200679566559 ft³/h |
| 3 Fluid ounces per hour | 0.00301019349839 ft³/h |
| 4 Fluid ounces per hour | 0.00401359133118 ft³/h |
| 5 Fluid ounces per hour | 0.00501698916398 ft³/h |
| 10 Fluid ounces per hour | 0.010033978328 ft³/h |
| 20 Fluid ounces per hour | 0.0200679566559 ft³/h |
| 25 Fluid ounces per hour | 0.0250849458199 ft³/h |
| 50 Fluid ounces per hour | 0.0501698916398 ft³/h |
| 100 Fluid ounces per hour | 0.10033978328 ft³/h |
| Reference | Fluid ounces per hour (fl oz/h) | Cubic feet per hour (ft³/h) |
|---|---|---|
| A domestic shower | 19005.3 fl oz/h | 19.0699 ft³/h |
| A kitchen tap | 21117 fl oz/h | 21.1888 ft³/h |
| A garden hose | 31675.6 fl oz/h | 31.7832 ft³/h |
| The Amazon river | 2.64808 × 1013 fl oz/h | 2.65708 × 1010 ft³/h |
The fluid ounce per hour is a unit of volumetric flow rate equal to one imperial fluid ounce passing a point every hour. Its symbol is fl oz/h. An imperial fluid ounce is 28.413 millilitres, so an hour at this rate delivers about two tablespoons — a rate slow enough that it is measured by what has collected, not by what is moving.
Slow feeding and slow dosing account for most of its use. A drip feeder on a bird cage, a wick humidifier, a fragrance diffuser and a slow-release fertiliser injector on a greenhouse line all move liquid at a few fluid ounces per hour, and the reservoir capacity divided by that rate gives the interval between refills.
Domestic appliances are described by it in older British literature. A paraffin heater consumes a few fluid ounces per hour, a wick lamp rather less, and an oil-filled stove was once sold with its consumption stated exactly this way so that a household could calculate how long a gallon would last through a winter evening.
Evaporation and leakage measurements fall here too. Water lost from an open tank, brake fluid seeping past a seal, or condensate collected from a small cooling coil are all quantified per hour, because that is the shortest period over which enough accumulates to measure in an ordinary graduated cylinder.
The unit's usefulness lies in matching the observation to the human timescale. Nobody watches a drip for a second; a technician checks a container after an hour, a shift or a night, and expressing the rate per hour lets the observed volume be divided by the elapsed hours with no further arithmetic.
For orientation, 160 fluid ounces make an imperial gallon, so one fluid ounce per hour fills a gallon in a little under a week. Thirty-five fluid ounces per hour is about a litre per hour, and sixty fluid ounces per hour is one fluid ounce per minute.
One fluid ounce per hour equals about 28.41 millilitres per hour, about 0.02841 litres per hour, or about 0.01667 fluid ounces per minute.
The cubic foot per hour is a unit of volumetric flow rate equal to one cubic foot passing a point every hour. Its symbol is ft³/h, and in the gas trades it is abbreviated CFH. It is the unit of fuel gas supply throughout North America, where every appliance and every pipe is sized by it.
Natural gas is billed and metered in cubic feet, so the hourly rate is what a gas fitter works with. A domestic furnace consumes 80 to 150 cubic feet per hour, a water heater 40, a cooking range 65, and a whole house at design conditions perhaps 250. A residential meter is rated at 250 CFH and the service pipe at rather more.
Pipe sizing tables are built entirely around this unit. Given a length of pipe, a diameter and an allowable pressure drop, the table returns a capacity in cubic feet per hour, and the fitter compares it against the sum of the appliance ratings on that branch. Undersize the pipe and the burners starve when everything runs at once; oversize it and the material cost rises for no benefit.
The unit converts easily into heat. Natural gas carries roughly 1,000 British thermal units per cubic foot, so a rate in cubic feet per hour is very nearly the same number in thousands of British thermal units per hour. An appliance rated 100,000 British thermal units per hour therefore burns about 100 cubic feet per hour, which is why the two figures appear together on every rating plate.
Propane behaves differently and is worth stating separately. It carries about 2,500 British thermal units per cubic foot, so the same appliance needs less than half the volumetric flow, and a pipe sized for natural gas is generously large for propane. Confusing the two is a classic and dangerous error in the trade.
Beyond fuel gas, the unit describes slow air and gas flows in imperial practice: purge lines, instrument air, small blowers and laboratory gas supplies. Sixty cubic feet per hour is one cubic foot per minute, and 35.31 cubic feet per hour is one cubic metre per hour.
One cubic foot per hour equals about 0.02832 cubic metres per hour, about 28.32 litres per hour, or about 0.01667 cubic feet per minute.