| Cubic inches per minute (in³/min) | Liters per hour (L/hour) |
|---|---|
| 1 Cubic inch per minute | 0.98322384 L/hour |
| 2 Cubic inches per minute | 1.96644768 L/hour |
| 3 Cubic inches per minute | 2.94967152 L/hour |
| 4 Cubic inches per minute | 3.93289536 L/hour |
| 5 Cubic inches per minute | 4.9161192 L/hour |
| 10 Cubic inches per minute | 9.8322384 L/hour |
| 20 Cubic inches per minute | 19.6644768 L/hour |
| 25 Cubic inches per minute | 24.580596 L/hour |
| 50 Cubic inches per minute | 49.161192 L/hour |
| 100 Cubic inches per minute | 98.322384 L/hour |
| Reference | Cubic inches per minute (in³/min) | Liters per hour (L/hour) |
|---|---|---|
| A domestic shower | 549.214 in³/min | 540 L/hour |
| A kitchen tap | 610.237 in³/min | 600 L/hour |
| A garden hose | 915.356 in³/min | 900 L/hour |
| The Amazon river | 7.65238 × 1011 in³/min | 7.524 × 1011 L/hour |
The cubic inch per minute is a unit of volumetric flow rate equal to one cubic inch passing a point every minute. Its symbol is in³/min. In the machine shop it is better known by its initials: MRR, the material removal rate, the single figure that says how fast a cutting process is turning solid metal into chips.
The calculation behind it is simple multiplication. Depth of cut times width of cut times feed rate gives the volume removed per minute, so a 0.2-inch depth at 1 inch wide with a feed of 30 inches per minute removes 6 cubic inches per minute. Every variable a machinist can change appears in that product, which is why it is the number used to compare one strategy against another.
Material decides what is achievable. Roughing aluminium on a rigid machine can exceed 100 cubic inches per minute, mild steel manages perhaps 10 to 20, stainless steel less, and nickel alloys used in turbine parts only a few. The limit is set by spindle power, by the rigidity of the setup and by the heat the tool can survive, in whichever order runs out first.
Spindle power connects directly to it. Each material has a specific cutting energy, roughly 1 horsepower per cubic inch per minute for steel and a third of that for aluminium, so a 20-horsepower spindle can sustain about 20 cubic inches per minute in steel. A quoted removal rate that exceeds the machine's power is arithmetic that the machine will settle in its own way.
Beyond cutting, the unit describes small imperial flows generally. Hydraulic pilot lines, lubrication systems, fuel injection test benches and adhesive dispensers on American equipment are all rated in cubic inches per minute, where the metric world would say millilitres per minute.
For scale, 61 cubic inches per minute is about a litre per minute, and 231 cubic inches per minute is exactly one US gallon per minute — the gallon being defined as 231 cubic inches. That exact relation is why hydraulic engineers move between the two units without a conversion table.
One cubic inch per minute equals about 16.39 cubic centimetres per minute, about 0.01667 cubic inches per second, or about 0.004329 US gallons per minute.
The litre per hour is a unit of volumetric flow rate equal to one litre passing a point every hour. Its symbol is L/h. It is the unit of slow, sustained flows — the ones too gradual to watch, where what matters is how much has moved by the end of a working day rather than what the stream looks like now.
Irrigation is its clearest home. A drip emitter is rated at 2, 4 or 8 litres per hour, and an orchard is designed by counting emitters: two hundred trees with two 4-litre emitters each draw 1,600 litres per hour, so a three-hour watering delivers 4.8 cubic metres. Because the emitters run for hours, the hourly figure is the one that maps directly onto the water budget.
Fuel consumption is quoted the same way whenever an engine runs at a steady load rather than travelling. A generator burns 2 to 5 litres per hour, a farm tractor 10 to 20, a large marine diesel several thousand. Litres per hour is the honest unit for these machines because litres per 100 kilometres means nothing to something that does not move.
Heating appliances follow. An oil boiler is rated by its burner nozzle in litres per hour, typically 1.5 to 3 for a house, and the figure multiplied by the heating value of the oil gives the heat output in kilowatts. A hot-water tap that produces 8 litres per minute is 480 litres per hour, which is why the same equipment carries both numbers in different parts of its documentation.
Laboratory and process work uses the unit for pumps that must run all day. Peristaltic dosing pumps for chlorination, water treatment and fermentation feeds are specified in litres per hour, often with a turndown range like 0.5 to 20, because the point of such a pump is to keep a slow rate constant for weeks.
Leaks and losses are described here too. A dripping tap loses a few litres per hour, which is trivial in a minute and a hundred litres by the next morning. Water utilities express network losses this way for the same reason: a slow rate compounded over the hours of a year is what turns an unnoticed defect into a measurable volume.
One litre per hour equals about 0.000278 litres per second, 0.01667 litres per minute, or 0.001 cubic metres per hour.