You can convert volume flow online for free in seconds: open the Volume Flow Converter, enter the value, and choose the units on both sides. The anchor conversion is simple to remember — 1 litre per second equals exactly 60 litres per minute and 3.6 cubic metres per hour, about 15.85 US gallons per minute, and about 2.119 cubic feet per minute (CFM). Every conversion in this guide is built from those four facts.
Volume flow causes more quiet mistakes than almost any other measurement, because it looks like volume and is not. A volume says how much space something fills. A volume flow says how fast that amount is moving — volume divided by time. Misread one for the other and a pump is specified ten times too large, a tank fill time is wrong by an hour, or an extractor is bought for a room it cannot clear. The five units the converter handles cover nearly everything practical work produces: litres per second and litres per minute for smaller equipment and laboratory work, cubic metres per hour for pumps and process plant, US gallons per minute for American datasheets, and cubic feet per minute for air handling. This guide explains where each factor comes from, works three examples in full, and shows the checks that catch a conversion before it costs money.
How Do You Convert Volume Flow Online, Step by Step?
- Open the converter. Go to the Volume Flow Converter with the datasheet, drawing or specification that gave you the figure.
- Confirm the figure really is a flow. A flow unit always names a volume and a time together — litres per second, gallons per minute. A figure in plain litres or plain gallons is a volume, not a flow, and it does not belong in this converter until you know the time it covers.
- Enter the value and choose its unit. Litres per second for compact equipment, cubic metres per hour for pumps and plant, US gallons per minute for American ratings, CFM for fans and air handling.
- Choose the unit your reader or calculation needs. The converted value appears using the exact factors in the table below.
- Sanity-check the direction. Moving to a bigger volume unit or a longer time unit makes the number smaller; moving to a smaller volume unit or a shorter time unit makes it bigger. Litres per minute always gives the largest-looking number of the five, and cubic metres per hour usually the smallest.
Volume Flow = Volume Divided by Time: Where Every Factor Comes From
Every factor in this converter is built from three definitions, and none of them needs to be taken on trust. First, time: one minute is 60 seconds and one hour is 60 minutes, which is why litres per second and litres per minute differ by exactly 60, and why litres per second and cubic metres per hour differ by exactly 3.6 — there are 3,600 seconds in an hour, and 3,600 litres is 3.6 cubic metres. Second, the US gallon: one US gallon is defined as 3.78541 litres, so converting any litre flow into US gallons means dividing by 3.78541. Worked through for the anchor: 1 litre per second is 60 litres per minute, and 60 divided by 3.78541 is 15.8503, which rounds to the 15.85 US gallons per minute quoted everywhere in this guide. Third, the cubic foot: one cubic foot is 28.3168 litres, so 1 litre per second is 60 litres per minute divided by 28.3168, which is 2.11888 cubic feet per minute, rounded to 2.119 CFM.
Notice what that structure means for checking your own work. Conversions inside the metric family — litres per second, litres per minute, cubic metres per hour — use round factors, so they should come out clean: if a metric-to-metric conversion produces an untidy number, the untidiness came from your starting figure, not the factor. Conversions that cross to US gallons or cubic feet produce untidy numbers naturally, because 3.78541 and 28.3168 are untidy definitions. Expect about 15.85 and about 2.119, and be suspicious of any source that quotes a suspiciously round figure for either bridge, such as 16 gallons or 2 CFM exactly — those are approximations wearing the clothes of exact factors.
| Conversion | Factor | Worked check |
|---|---|---|
| Litres/second to litres/minute | Multiply by 60 | 1 L/s = 60 L/min |
| Litres/second to cubic metres/hour | Multiply by 3.6 | 1 L/s = 3.6 m³/h |
| Litres/second to US gallons/minute | Multiply by about 15.8503 | 1 L/s ≈ 15.85 US gal/min |
| Litres/second to cubic feet/minute | Multiply by about 2.11888 | 1 L/s ≈ 2.119 CFM |
| Cubic metres/hour to litres/second | Divide by 3.6 | 36 m³/h = 10 L/s |
| US gallons/minute to litres/second | Divide by about 15.8503 | 158.5 US gal/min ≈ 10 L/s |
Worked Examples: A Pump Rating in Every Unit
Example 1 — one pump, five ways of saying the same flow. A pump is rated at 10 litres per second. In litres per minute that is 10 × 60 = 600 L/min. In cubic metres per hour it is 10 × 3.6 = 36 m³/h. In US gallons per minute it is 10 × 15.8503 = about 158.5 US gal/min. In cubic feet per minute it is 10 × 2.11888 = about 21.19 CFM. Five numbers, one physical flow: 600, 36, 158.5 and 21.19 all describe exactly the same pump, which is why comparing raw digits across units — deciding 600 must be a bigger pump than 36 — is the classic error in this topic.
Example 2 — a plant-room flow quoted in cubic metres per hour. A specification calls for 90 cubic metres per hour. In litres per second that is 90 ÷ 3.6 = 25 L/s. In litres per minute it is 25 × 60 = 1,500 L/min. In US gallons per minute it is 25 × 15.8503 = about 396.26 US gal/min. In cubic feet per minute it is 25 × 2.11888 = about 52.97 CFM. The round result in litres per second — exactly 25 — is the signature of a clean metric conversion, and it confirms the division was done the right way round.
Example 3 — an American rating brought into metric. A US datasheet rates a pump at 250 US gallons per minute. In litres per second that is 250 ÷ 15.8503 = about 15.77 L/s. In cubic metres per hour it is 15.77 × 3.6 = about 56.78 m³/h. Notice the two-step habit: convert into one metric unit first, check the size feels right against the anchor — 250 gallons a minute should be a substantial pump, and about 16 litres every second is substantial — then convert onward to whichever metric unit the drawing needs.
One litre per second expressed in each unit — hover or tap each bar for details.
The chart shows the anchor conversion itself, and its proportions carry the main lesson of this topic. The bar for litres per minute stretches the full width because the minute is a long time unit paired with a small volume unit, so the number inflates. Cubic metres per hour pairs a large volume unit with a long time unit, and the two effects nearly cancel, leaving a small, tidy number. US gallons per minute sits between the two, and CFM sits near the bottom because a cubic foot is a large volume — nearly 30 litres — even though the minute is short. When two quotes for the same job arrive in different units, this is the picture to hold in mind before deciding one of them must be wrong: the numbers are supposed to look wildly different.
Which Unit Will You Meet Where?
| Situation | Unit you will usually see | Watch for |
|---|---|---|
| Pumps and process plant | m³/h or L/s | Large plant in cubic metres per hour; smaller equipment in litres per second |
| United States datasheets | US gallons per minute | Confirm the gallon is a US gallon, not an imperial one |
| Fans, extractors and HVAC air | CFM (cubic feet per minute) | Air flows are large numbers; 1 L/s is only about 2.119 CFM |
| Laboratory and dosing work | L/min or L/s | Small flows; a misplaced decimal is a tenfold dosing error |
| Plumbing and water services | L/s or L/min | Fixture and pipe ratings mix the two; the factor between them is 60 |
Five Mistakes That Spoil Volume Flow Conversions
- Comparing raw numbers across units. A 600 L/min pump and a 36 m³/h pump are the same pump. Convert before you compare, every time, even when the numbers look close enough to judge by eye.
- Dropping the time unit halfway through. A calculation that starts in litres per second and quietly finishes in litres per minute is wrong by a factor of 60. Write the full unit beside every number until the answer is final.
- Assuming every gallon is a US gallon. The converter uses US gallons at 3.78541 litres. Imperial gallons are larger, so a rating in imperial gallons per minute converts to a bigger metric flow than the same digits in US gallons.
- Converting a volume as if it were a flow. Five hundred litres in a tank says nothing about flow until a time is attached. If the source figure has no time unit, the missing information is the first problem to solve.
- Rounding the bridge factors too early. Using 16 instead of 15.8503 for gallons, or 2 instead of 2.11888 for CFM, is fine for a rough estimate and wrong for a specification. Convert with the full factor, then round the final answer.
Conclusion: Anchor Everything to One Litre per Second
Volume flow conversion becomes self-checking the moment the anchor is memorised: 1 litre per second is 60 litres per minute, 3.6 cubic metres per hour, about 15.85 US gallons per minute and about 2.119 CFM. Any converted figure can be tested against that picture — litres per minute should look big, cubic metres per hour small, gallons in between — and a result that breaks the pattern has almost always divided where it should have multiplied. Keep the time unit attached to every number, confirm which gallon a datasheet means, and let the Volume Flow Converter do the arithmetic. The companion tools sit close by: the volume converter handles the amounts themselves when no time is involved, and the speed converter covers the other common per-time measurement. For the background reading, our guide to converting volume units online covers litres, gallons and cubic metres in depth, and our guide to converting speed units online shows the same per-time logic applied to movement.
Pump, HVAC and process-equipment websites lose enquiries when a specification table states flows in units half the readership cannot read. If your product pages quote litres per second to buyers who think in gallons per minute or CFM, book a free consultation with Asad Webs and mention the pages involved; clear dual-unit presentation is a small fix that prevents misordered equipment.
Frequently Asked Questions
What is the difference between volume and volume flow?
Volume is an amount on its own — a tank holding 500 litres. Volume flow is that amount moving over time — a pump delivering 500 litres every minute. The units give it away: flow units always pair a volume with a time, like litres per second or cubic metres per hour, while plain litres, gallons or cubic metres carry no time at all.
How do I convert litres per second to cubic metres per hour?
Multiply by 3.6. One litre per second is 60 litres per minute, and 60 litres is 0.06 cubic metres, so 0.06 times 60 minutes gives 3.6 cubic metres per hour. To go back from cubic metres per hour to litres per second, divide by 3.6 instead.
How do I convert litres per second to US gallons per minute?
Multiply by about 15.85. One US gallon is 3.78541 litres, so one litre per second is 60 litres per minute divided by 3.78541, which is about 15.85 US gallons per minute. Ten litres per second is therefore about 158.5 US gallons per minute.
What does CFM mean, and where is it used?
CFM is cubic feet per minute, the standard volume flow unit for air handling in the United States: fans, extractors, compressors and HVAC equipment are usually rated in CFM. One litre per second is about 2.119 CFM, so a 1,000 CFM extractor is moving roughly 472 litres per second of air.
Are US gallons and imperial gallons the same in flow ratings?
No, and the converter on this page uses US gallons. An imperial gallon is larger than a US gallon, so a rating quoted in imperial gallons per minute describes a bigger flow than the same number in US gallons per minute. Always check which gallon a datasheet means before converting, especially on older British equipment.
How do I turn a flow rate into a total volume?
Multiply the flow by the time it runs, keeping the time unit matched. A flow of 10 litres per second running for 30 seconds delivers 300 litres. A flow of 36 cubic metres per hour running for 2 hours delivers 72 cubic metres. If the time is in a different unit from the flow, convert one of them first.
Why do pump datasheets use so many different flow units?
Because pumps are sold into different industries and countries at once. European process work favours cubic metres per hour, laboratories and smaller equipment favour litres per second or per minute, and United States datasheets favour gallons per minute. The physical flow is identical; only the ruler changes, which is exactly what the converter handles.
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