Flow Rate Converter
m³/h, L/s, L/min and GPM — every unit at once.
Quick answer
With the default inputs: Value 10 · From unit Cubic metre per hour · To unit Litre per secondConverted value 2.7778 L/s
Edit the inputs below to recalculate.Inputs
Result
Converted value
2.7778L/s
| Cubic metre per hour | 10m³/h |
| Cubic metre per second | 0.002778m³/s |
| Litre per second | 2.7778L/s |
| Litre per minute | 166.6667L/min |
| Litre per hour | 10000.00L/h |
| US gallon per minute | 44.0286GPM |
| US gallon per hour | 2641.72GPH |
| Cubic foot per minute | 5.8858CFM |
Conversions use the US gallon (3.785 L). Imperial gallon flows are 20% larger; always confirm on imported equipment.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Base | 1 m³/h = 1000 L/h = 0.2778 L/s |
| Per second | 1 L/s = 60 L/min = 3.6 m³/h |
| US units | 1 GPM = 3.785 L/min = 0.2271 m³/h |
| Air | 1 CFM = 1.699 m³/h |
| Pipe sizing | Q = A × v with A = πd²/4 |
10 m³/h is 2.778 L/s, 166.67 L/min, 44.03 GPM or 5.886 CFM. A DN50 pipe at 1.5 m/s carries about 10.6 m³/h — the same order.
Flow rate unit reference
| Unit | Symbol | In m³/h | In L/s | Typical use |
|---|---|---|---|---|
| Cubic metre per hour | m³/h | 1 | 0.2778 | Pumps, cooling towers |
| Cubic metre per second | m³/s | 3600 | 1000 | Rivers, large flows |
| Litre per second | L/s | 3.6 | 1 | Supply design |
| Litre per minute | L/min | 0.06 | 0.01667 | Terminal use |
| US gallon per minute | GPM | 0.2271 | 0.0631 | Imported equipment |
| Cubic foot per minute | CFM | 1.699 | 0.4719 | Ventilation, fans |
How to work it out
- Separate volumetric from mass flow first. m³/h and L/s are volumetric; t/h is mass, linked by density (water at 1 t/m³). Pump and fan data sheets use volumetric flow.
- Metric backbone: 1 m³/h = 1000 L/h = 0.2778 L/s, and conversely 1 L/s = 3.6 m³/h = 60 L/min. That 3.6 is the most-used factor in plumbing calculation.
- Imperial: 1 GPM (US gallon per minute) = 3.785 L/min = 0.2271 m³/h, and 1 GPH is GPM × 60. Imported pumps and fire equipment are rated in GPM.
- Airflow: 1 CFM = 1.699 m³/h = 0.4719 L/s. Air conditioning, cleanrooms and imported fans are often rated in CFM.
- Sizing the pipe: Q = A × v with A = πd²/4, so flow and velocity give the bore, and bore and velocity give the flow. Convert to m³/s before substituting — a unit slip here is a factor of 3600.
- Check: 10 m³/h is about 2.78 L/s or 44 GPM. A wrong order means the wrong system.
Where it goes wrong
- Substituting L/s directly into Q = A × v. The formula needs m³/s and 1 L/s is 0.001 m³/s; omitting that gives a bore 31.6 times too large (√1000).
- Reversing the m³/h and L/s direction. 1 L/s is 3.6 m³/h, not 1/3.6. Ten L/s is 36 m³/h, and using 2.78 understates by a factor of 13.
- Converting GPM with UK gallons. GPM defaults to US gallons at 3.785 L, while British data may use 4.546 L — 20% apart.
- Treating CFM as equal to m³/h. One CFM is about 1.7 m³/h, so a 1:1 assumption selects a fan 40% too small and starves the system.
- Confusing flow with velocity. Flow is m³/h and velocity m/s, separated by an area. Selecting a pump on velocity is a basic error that still happens on site.
Material and cost
Flow unit errors are order-of-magnitude errors in pump and pipe selection. A 10 m³/h duty read as 10 L/s buys equipment 3.6 times too large — tens of thousands wasted and permanently inefficient running. The reverse leaves the system short of flow, and in fire systems that simply fails acceptance.
On site
- Remember two plumbing conversions: 1 L/s = 3.6 m³/h and 1 m³/h = 0.278 L/s. They cover everyday work.
- Quick flow-to-bore judgement at 1.2 m/s: DN15 about 0.15 L/s, DN20 about 0.25, DN25 about 0.4, DN50 about 1.5.
- For chilled water, one refrigeration ton (3.517 kW) needs roughly 0.6 m³/h at a 5°C difference — a fast way to size mains.
- Airflow from air changes: room volume × air changes per hour. Dwellings need 1-2, offices 4-6, kitchens 15-30 — quicker than tables.
Basis
- GB/T 3100-3102 Quantities and units series
- GB 50015-2019 Standard for design of building water supply and drainage, hydraulic calculation
- GB 50736-2012 Design code for heating, ventilation and air conditioning of civil buildings, ventilation
FAQ
Why do pumps come in m³/h when pipes are sized in L/s?
Different habits: pump makers rate hourly output while hydraulic tables are per second, a factor of 3.6. Convert everything to L/s before reading tables, or 10 m³/h gets mistaken for 10 L/s and the pipe comes out 2.7 times too big.
What is an economic water velocity?
Usually 1.0-1.5 m/s, 0.6-1.0 below DN50 and 1.2-2.0 above DN100. Too slow and sediment settles with long stagnation; too fast and head loss grows with the square of velocity, bringing noise and erosion. Fire mains may run to 2.5 m/s.
How do I convert GPM to m³/h quickly?
Multiply by 0.227, or roughly 0.23; the other way, 1 m³/h ≈ 4.4 GPM. Imported pumps and cooling towers rate flow in GPM while domestic fittings are chosen in m³/h, and a conversion slip shows up as insufficient cooling water and high-temperature alarms.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Flow Rate Converter. 2026-10-25. https://jianzhujisuan.com/en/unit-flow
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.