Volumetric Flow Rate Converter (L/min ↔ gal/min ↔ m³/h ↔ ft³/s)
Enter a flow rate in any common unit and the tool converts to twelve others at once — SI m³/s and m³/h, lab and industry favourites L/s, L/min, L/h, North-American US gpm / gph, imperial UK gpm, HVAC and aerospace ft³/s (cfs) and ft³/min (cfm), mechanical-engineering in³/s, plus the petroleum-industry bbl/day. All factors come from NIST SP 811 exact definitions; everything runs locally in your browser — no API or data leaves the page.
Please enter zero or a positive number.
In other units
- m³/s (SI)
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- m³/h
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- L/s
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- L/min
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- L/h
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- US gal/min (gpm)
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- US gal/h
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- UK gal/min (imperial)
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- ft³/s (cfs)
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- ft³/min (cfm)
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- in³/s
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- barrel/day (bbl/d, 42 US gal)
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Formula
All conversions pass through m³/s as the canonical unit then go out to the target. 1 m³/s = 1000 L/s = 60 000 L/min 1 m³/h = 1 / 3600 m³/s ≈ 2.778 × 10⁻⁴ m³/s 1 L/min = 1 / 60 000 m³/s ≈ 1.667 × 10⁻⁵ m³/s 1 US gal/min = 3.785411784 × 10⁻³ / 60 ≈ 6.309 × 10⁻⁵ m³/s 1 UK gal/min = 4.54609 × 10⁻³ / 60 ≈ 7.577 × 10⁻⁵ m³/s 1 ft³/s (cfs) = 0.028316846592 m³/s 1 ft³/min (cfm) = 1 cfs / 60 1 bbl/day = 42 US gal / 86 400 s ≈ 1.840 × 10⁻⁶ m³/s
- · All conversion factors come from NIST SP 811 (2008) exact definitions: 1 US gallon = 3.785411784 L (exact since 1893); 1 imperial gallon = 4.54609 L (exact, UK Weights and Measures Act 1985); 1 ft = 0.3048 m; 1 in = 0.0254 m; 1 oil barrel = 42 US gal = 158.987294928 L.
- · Memorise "1 US gpm ≈ 3.785 L/min ≈ 0.063 L/s" as a mental anchor. A split-AC condensate line drips 0.5–2 L/h (tiny); a bathroom tap runs 6–8 L/min; a tankless water heater 12–18 L/min; a garden sprinkler 8–15 L/min; a fire hydrant 1 000–2 000 L/min (~250–500 US gpm).
- · US gpm vs UK gpm differ by ~20.1 % — US gallon 3.785 L vs imperial gallon 4.546 L. Always confirm which gallon is meant when sourcing pumps or fire equipment internationally.
- · HVAC: cfm is North-American standard, 1 cfs = 60 cfm. European HVAC uses m³/h: 1 m³/h ≈ 0.589 cfm. Living-room exhaust target: 6–10 air changes/hour × room volume ÷ 60 ≈ required cfm.
- · Petroleum: bbl/day is a flow rate, not a tank size. 1 000 bbl/d ≈ 6.624 m³/h ≈ 1.840 L/s. Be careful — the oil barrel (42 US gal) differs from beer (31 US gal) and wine (31.5 US gal) barrels.
- · Mass flow rate = volumetric flow × density. This tool handles volume only; for kg/s, multiply by the fluid density (water ≈ 1000 kg/m³, air 1.2 kg/m³, fuels 700–900 kg/m³). Use this site's Density Converter alongside.
- · Pipe sizing: velocity v (m/s) = Q (m³/s) ÷ A (m²). Example: 100 L/min = 1.667 × 10⁻³ m³/s through a 25 mm pipe (A ≈ 4.91 × 10⁻⁴ m²) gives ~3.4 m/s — near the upper limit for water (2–3 m/s avoids noise and erosion).
- · References: (1) NIST SP 811 (2008) "Guide for the Use of the International System of Units"; (2) ASHRAE Handbook—HVAC Applications; (3) API Std 2554 for petroleum bbl/day usage.
Frequently asked
How do I convert gpm to lpm (and back)?
It depends on US vs UK. US (North-American pumps, residential, automotive): 1 US gpm = 3.785411784 L/min (exact) ≈ 3.785 L/min; inverse 1 L/min ≈ 0.2642 US gpm. UK / imperial (UK, Commonwealth, some older Malaysian specs): 1 UK gpm = 4.54609 L/min (exact) ≈ 4.546 L/min; inverse 1 L/min ≈ 0.2200 UK gpm. The ~20 % gap matters: a "10 US gpm" pump actually delivers 37.85 L/min, but if you mistakenly read it as imperial gpm you would expect 45.46 L/min — a 7.6 L/min error. This tool shows all three numbers (US gpm, UK gpm, L/min) side-by-side for instant cross-check. Rule of thumb: for < 100 L/min keep L/min for intuition; ≥ 100 L/min switch to m³/h (1 m³/h = 16.67 L/min); commercial HVAC and fire systems prefer L/s plus cfs / cfm.
How are cfm and cfs used in HVAC?
cfm (ft³/min) is the workaday North-American HVAC unit — used in fan specs, duct sizing and exhaust airflow. cfs (ft³/s) = 60 cfm, used for large air handlers, lab fume hoods and outdoor air-quality studies. Europe and Asia prefer m³/h (1 cfm ≈ 1.699 m³/h) or L/s (1 cfm ≈ 0.472 L/s). Practical magnitudes: (a) kitchen range hood 600–1 200 cfm (strong exhaust); (b) bathroom fan 50–100 cfm; (c) whole-house ventilation ≥ 0.35 air-changes/hr × house volume ÷ 60 — e.g. 1 200 ft² × 8 ft ceiling = 9 600 ft³ × 0.35 = 3 360 ft³/hr ≈ 56 cfm continuous; (d) commercial offices typically 6–10 air-changes/hr. ASHRAE 62.1 sets minimum outdoor air at 5–10 cfm/person (residential) to 15–20 cfm/person (offices). Use this tool to swap cfm ↔ L/s ↔ m³/h when cross-referencing international standards.
Anything tricky about flow units in fire-protection systems?
Yes — unit choice can swing fire-system design significantly. North-American NFPA 13 uses US gpm (the sprinkler K-factor formula Q = K √p has p in psi, Q in gpm). Europe and Asia mostly use L/min (EN 12845); some consultants prefer m³/h. Old Commonwealth references sometimes used UK gpm — never assume. Reference magnitudes: (a) fire-hydrant flow 250–1 000 US gpm (≈ 950–3 800 L/min); (b) sprinkler head 20–60 US gpm (≈ 75–230 L/min); (c) high-rise standpipe needs 500 US gpm at the lowest floor to keep pressure. If you are reading NFPA tables but your system docs are in L/min, convert before doing K-factor maths. This tool shows US gpm + L/min + m³/h together for fast cross-checks. A 20 % flow-rate misread can leave water tanks, pumps and reservoir hold-times out of code — the consequences are serious.
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