| Cubic inches per second (in³/s) | Cubic meters per hour (m³/h) |
|---|---|
| 1 Cubic inch per second | 0.0589934304 m³/h |
| 2 Cubic inches per second | 0.1179868608 m³/h |
| 3 Cubic inches per second | 0.1769802912 m³/h |
| 4 Cubic inches per second | 0.2359737216 m³/h |
| 5 Cubic inches per second | 0.294967152 m³/h |
| 10 Cubic inches per second | 0.589934304 m³/h |
| 20 Cubic inches per second | 1.179868608 m³/h |
| 25 Cubic inches per second | 1.47483576 m³/h |
| 50 Cubic inches per second | 2.94967152 m³/h |
| 100 Cubic inches per second | 5.89934304 m³/h |
| Reference | Cubic inches per second (in³/s) | Cubic meters per hour (m³/h) |
|---|---|---|
| A domestic shower | 9.15356 in³/s | 0.54 m³/h |
| A kitchen tap | 10.1706 in³/s | 0.6 m³/h |
| A garden hose | 15.2559 in³/s | 0.9 m³/h |
| The Amazon river | 1.2754 × 1010 in³/s | 752400000 m³/h |
The cubic inch per second is a unit of volumetric flow rate equal to one cubic inch passing a point every second. Its symbol is in³/s. A cubic inch is 16.387 cubic centimetres, a little over a tablespoon, so this unit describes the modest but visible flows of imperial engineering practice.
Hydraulics is where it survives most strongly. American hydraulic pumps and cylinders are still catalogued in inches, and a cylinder's speed follows directly from the flow divided by the piston area: a 2-inch bore cylinder has an area of 3.14 square inches, so 31.4 cubic inches per second extends it at 10 inches per second. Working in inches throughout avoids converting the bore, the stroke and the flow separately.
Machining uses the same idea for material removal. A milling cutter taking a 0.1-inch depth at 0.5 inch width and 20 inches per minute of feed removes one cubic inch per minute, and a modern machining centre roughing aluminium can exceed twenty. Tool manufacturers publish removal rates in these units because their customers' machines are dimensioned that way.
Small engines and pumps carry the unit too. An engine's displacement in cubic inches, multiplied by its speed, gives the air it swallows: a 350 cubic inch V8 at 3,000 revolutions per minute ingests 525,000 cubic inches a minute, or about 8,750 per second, ideal efficiency assumed. The old American habit of naming engines by cubic inches is the same measurement standing still rather than flowing.
Metering and dispensing in imperial industries follow. Adhesive dispensers, lubricators and grease systems on American plant are specified in cubic inches per second or per minute, and a shot of grease from an automatic lubricator is quoted in cubic inches per cycle, which the cycle time converts into a rate.
For a sense of scale, 61 cubic inches per second is about a litre per second, and one cubic inch per second fills a US gallon in a little under four minutes. That is roughly the rate of a garden tap opened a quarter turn, which makes the unit easy to picture despite its unfamiliarity outside the imperial trades.
One cubic inch per second equals about 16.39 cubic centimetres per second, 0.01639 litres per second, or about 0.2597 US gallons per minute.
The cubic metre per hour is a unit of volumetric flow rate equal to one cubic metre passing a point every hour. Its symbol is m³/h. It is the commercial unit of flow: the one that appears on water bills, gas meters, pump curves and ventilation schedules, because a cubic metre per hour multiplied by the hours of operation gives the volume that is actually paid for.
Domestic water and gas meters read in cubic metres, and the meter's rating is a flow in cubic metres per hour — typically 1.5 or 2.5 for a house, meaning the maximum continuous flow it can measure accurately. A gas meter marked G4 passes 6 cubic metres per hour, which at the calorific value of natural gas is roughly 63 kilowatts, comfortably more than a domestic boiler needs.
Pumps are sold by their curve, and the curve's horizontal axis is almost always cubic metres per hour. A domestic booster pump delivers 2 to 5, a swimming-pool pump 10 to 20, an irrigation pump 50 to 200, and a large water-supply pump thousands. Reading the curve at the required flow gives the head the pump can produce and the power it will draw.
Ventilation is scheduled in the same unit across much of Europe. A dwelling requires roughly 0.5 air changes an hour, so a 250 cubic metre flat needs about 125 cubic metres per hour of fresh air; a restaurant kitchen hood may need 3,000, and a laboratory fume cupboard around 1,000 each. Since the room volume is in cubic metres, using the hour as the time base makes the arithmetic immediate.
Industrial process flows are quoted here whether the fluid is liquid or gas. Cooling towers, boiler feedwater, effluent treatment and compressed-air dryers all carry ratings in cubic metres per hour, and district heating substations are sized from the flow needed to carry the heat at a given temperature difference.
Its relation to the SI unit is a division by 3,600. One cubic metre per second is 3,600 cubic metres per hour, which is why river flows look enormous in this unit and why hydrologists avoid it. The hour is the right base for equipment that runs continuously and is billed monthly.
One cubic metre per hour equals about 0.000278 cubic metres per second, 1,000 litres per hour, or about 4.403 US gallons per minute.