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GPM Converter (gallons per minute, barrels per day, m³/day)

Type a value — the result and every other unit update as you type.

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Understanding the GPM converter — concept and principle

GPM (gallons per minute) is the usual flow unit for pumps, wells, faucets and irrigation in the United States, while the oil industry uses barrels per day and most other countries use litres per minute or cubic metres per hour or per day. This converter switches between US GPM, UK GPM, barrels per day (BPD), L/min, m³/h and m³/day.

Gallons per minute to litres and barrels10 US gallons a minute is 37.85 litres a minute. Over 1,440 minutes that is 14,400 gallons a day: 342.9 barrels of 42 gallons, or 54.51 cubic metres.10 gallons a minute, all day long10 US galevery minute= 37.85 L/min× 1,440 min a day= 14,400 US gallons a day342.9 BPD÷ 42 gal barrel54.51 m³/day× 3.785 ÷ 1,00010 GPM = 37.85 L/min
10 GPM = 37.85 L/min, which adds up to 342.9 barrels or 54.51 m³ a day.

How it is calculated

The value is converted to US GPM and then to the target unit: result = value × (US GPM per source unit) ÷ (US GPM per target unit). The underlying definitions are:

So 1 US GPM = 3.785411784 L/min = 0.2271 m³/h = 5.451 m³/day = 34.2857 BPD.

The principle

A flow rate is a volume per unit of time. Converting it is a matter of converting the volume (gallons to litres or barrels) and the time (minutes to hours or days) and multiplying the two factors. For barrels per day, a barrel is 42 gallons and a day is 1,440 minutes, so 1 GPM equals 1,440 ÷ 42 = 34.2857 barrels per day. All factors are fixed definitions, so the conversion is exact and does not depend on the liquid.

Worked example

  1. Inputs: 10 US GPM, convert to L/min.
  2. 10 × 3.785411784 = 37.85411784 L/min.
  3. In m³/h: 37.85411784 × 60 ÷ 1,000 = 2.27124707 m³/h.
  4. In m³/day: 37.85411784 × 1,440 ÷ 1,000 = 54.50992969 m³/day.
  5. In BPD: 10 × 1,440 ÷ 42 = 342.8571429 BPD; in UK GPM: 8.326741846.

How to read the result

Typical figures help put a result in context: a household tap often runs at roughly 6 to 12 L/min, a garden hose at around 10 to 20 L/min, and a domestic well pump is commonly sized in single or low double-digit GPM. Check whether a pump rating is at zero head (free flow) or at a stated head, because delivered flow drops as the pump lifts water higher or pushes it through longer pipe.

Common mistakes

Keep in mind: The unit conversion is exact, but pump and well performance depend on head, pipe size and water level. For sizing pumps, wells or plumbing, use the maker's pump curve and local codes, and consult a qualified professional.

Frequently asked questions

How do I convert GPM to L/min?

Multiply by 3.785411784. For example, 5 GPM ≈ 18.93 L/min.

How many barrels per day is 1 GPM?

34.2857 BPD, because 1,440 minutes ÷ 42 gallons per barrel.

Does the type of liquid change the conversion?

No. Volume flow converts the same way for water, oil or fuel; only mass flow depends on density.

Sources: NIST Handbook 44, Appendix C (General Tables of Units of Measurement) · NIST Special Publication 811 (2008), Appendix B

Checked 8 Nov 2026. Factors from the SI Brochure (BIPM, 9th ed.) and NIST Special Publication 811 (2008), Appendix B.

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