Gallons per Hour to Litres per Hour Converter | Free gal/h to L/h Calculator

💧 Free Online Flow Rate Converter

Gallons per Hour to Litres per Hour Converter

Instantly Convert gal/h ↔ L/h — US & Imperial Gallons Supported

Convert gallons per hour to litres per hour (gal/h → L/h) or litres per hour to gallons per hour (L/h → gal/h) instantly. Supports both US and Imperial gallons — with formula breakdown, reference tables, and real-world examples. Free, no sign-up needed.

✅ gal/h → L/h

✅ L/h → gal/h

✅ US & Imperial

✅ Exact Formula

Gallons per Hour to Litres per Hour (gal/h to L/h) Converter

Gallons per hour (gal/h) and litres per hour (L/h) are both units of volumetric flow rate — measuring how much liquid passes a point in one hour. Our converter handles both directions and both gallon types (US and Imperial) using exact conversion factors, making it accurate for fuel systems, pumps, irrigation, and industrial applications.

🇺🇸 What is a US Gallon per Hour?

The US gallon per hour (US gal/h or GPH) measures liquid flow using the US customary gallon, which equals exactly 3.785411784 litres. It is the standard flow rate unit in the United States for fuel systems, water pumps, irrigation, and engine fuel consumption. The US gallon is about 17% smaller than the Imperial gallon used in the UK.

🇬🇧 What is an Imperial Gallon per Hour?

The Imperial gallon per hour (Imp gal/h) uses the British Imperial gallon, defined as exactly 4.54609 litres. It is used in the United Kingdom, Canada (historically), and some Commonwealth countries for measuring fuel consumption and flow rates. The Imperial gallon is larger than the US gallon — 1 Imperial gal = 1.20095 US gallons.

💧 What is a Litre per Hour?

The litre per hour (L/h) is the standard metric unit of volumetric flow rate, used worldwide in engineering, science, and industry. It measures how many litres of liquid pass a point in one hour. One litre per hour equals 0.264172 US gal/h or 0.219969 Imperial gal/h. It is the most common flow rate unit outside the United States.

💧 Gallons per Hour ↔ Litres per Hour Converter

Select gallon type, choose direction, enter your value, and get an instant result

Value in Gallons/h (US gal/h)

Result in Litres/h (L/h)

Converted Value

— L/h

—

Litres/min

—

Litres/day

—

m³/hour

—

mL/second

—

Gallons per Hour to Litres per Hour Formula

The conversion between gallons per hour and litres per hour uses the exact volume conversion factor for the gallon type being used. The US and Imperial gallon have different defined values, so the two formulas give different results. Both are exact by international definition — no approximation is involved.

🇺🇸 US Gallons per Hour → Litres per Hour

L/h = US gal/h × 3.785411784

Example: 10 US gal/h × 3.785411784 = 37.854 L/h

Example: 100 US gal/h × 3.785411784 = 378.541 L/h

🇬🇧 Imperial Gallons per Hour → Litres per Hour

L/h = Imp gal/h × 4.54609

Example: 10 Imp gal/h × 4.54609 = 45.461 L/h

Example: 100 Imp gal/h × 4.54609 = 454.609 L/h

🔄 Litres per Hour → Gallons per Hour (Reverse)

US gal/h = L/h ÷ 3.785411784 (= L/h × 0.264172)

Imp gal/h = L/h ÷ 4.54609 (= L/h × 0.219969)

Example: 100 L/h ÷ 3.785411784 = 26.417 US gal/h

    💡 Quick Mental Estimate: For US gallons, multiply by roughly
    3.8 to get litres per hour (accurate to within 0.4%).
    For Imperial gallons, multiply by roughly 4.5.
    Example: 20 US gal/h × 3.8 ≈ 76 L/h (exact: 75.708 L/h).
    Always use the full conversion factor for precision work.
  

⚡ Quick Reference — US Gallons per Hour to Litres per Hour

1 US gal/h3.785 L/h

2 US gal/h7.571 L/h

5 US gal/h18.927 L/h

10 US gal/h37.854 L/h

25 US gal/h94.635 L/h

50 US gal/h189.271 L/h

100 US gal/h378.541 L/h

500 US gal/h1892.706 L/h

Real-World Flow Rates in Gallons & Litres per Hour

The chart below shows approximate flow rates of common real-world devices and systems, expressed in litres per hour. These figures help put gal/h to L/h conversions into practical context across domestic, agricultural, and industrial applications.

💧 Common Real-World Flow Rates (Litres per Hour)

Drip Irrigation

~4 L/h

Washing Machine

~50 L/h

Garden Hose

~1,000 L/h

Car Engine (idle)

~2–4 L/h

Diesel Generator

~12 L/h

Home Pump (domestic)

~3,000 L/h

Industrial Pump

50,000+ L/h

📌 Values are approximate typical figures. Actual flow rates vary by model, pressure, and operating conditions. To convert any L/h value to US gal/h, divide by 3.785411784.

US Gallons per Hour to Litres per Hour Conversion Table

The table below lists common US gal/h values converted to L/h, along with equivalent flow rates in other useful units. All values use the exact factor: 1 US gal = 3.785411784 litres.

US gal/h (GPH)	Litres/h (L/h)	Litres/min	m³/h	Common Context
0.5 US gal/h	1.893 L/h	0.032 L/min	0.00189 m³/h	Slow drip / fuel injector
1 US gal/h	3.785 L/h	0.063 L/min	0.00379 m³/h	Small fuel burner
2 US gal/h	7.571 L/h	0.126 L/min	0.00757 m³/h	Oil heating burner
5 US gal/h	18.927 L/h	0.315 L/min	0.01893 m³/h	Small generator fuel use
10 US gal/h	37.854 L/h	0.631 L/min	0.03785 m³/h	Medium generator
15 US gal/h	56.781 L/h	0.946 L/min	0.05678 m³/h	Large diesel generator
20 US gal/h	75.708 L/h	1.262 L/min	0.07571 m³/h	Boat outboard engine
25 US gal/h	94.635 L/h	1.577 L/min	0.09464 m³/h	Small irrigation pump
50 US gal/h	189.271 L/h	3.155 L/min	0.18927 m³/h	Medium pump system
100 US gal/h	378.541 L/h	6.309 L/min	0.37854 m³/h	Large agricultural sprinkler
200 US gal/h	757.082 L/h	12.618 L/min	0.75708 m³/h	Industrial flow system
500 US gal/h	1892.706 L/h	31.545 L/min	1.89271 m³/h	Large commercial pump
1000 US gal/h	3785.412 L/h	63.090 L/min	3.78541 m³/h	Municipal water system

Imperial Gallons per Hour to Litres per Hour Conversion Table

The table below shows Imperial gal/h values converted to litres per hour. All values use the exact factor: 1 Imperial gallon = 4.54609 litres, as defined by international agreement. Note that Imperial values are always larger than equivalent US values.

Imp gal/h	Litres/h (L/h)	US gal/h equiv.	Litres/min
1 Imp gal/h	4.546 L/h	1.201 US gal/h	0.076 L/min
2 Imp gal/h	9.092 L/h	2.401 US gal/h	0.152 L/min
5 Imp gal/h	22.730 L/h	6.003 US gal/h	0.379 L/min
10 Imp gal/h	45.461 L/h	12.009 US gal/h	0.758 L/min
20 Imp gal/h	90.922 L/h	24.019 US gal/h	1.515 L/min
50 Imp gal/h	227.305 L/h	60.047 US gal/h	3.789 L/min
100 Imp gal/h	454.609 L/h	120.095 US gal/h	7.577 L/min
200 Imp gal/h	909.218 L/h	240.190 US gal/h	15.154 L/min
500 Imp gal/h	2273.045 L/h	600.475 US gal/h	37.884 L/min
1000 Imp gal/h	4546.090 L/h	1200.950 US gal/h	75.768 L/min

When Do You Need to Convert Gallons per Hour to Litres per Hour?

The gallons-per-hour to litres-per-hour conversion is needed across a wide range of industries and everyday applications — anywhere flow rates are measured or specified.

⛽ Fuel Consumption & Engines

Engine fuel consumption is often rated in gallons per hour (GPH) in the US — particularly for marine engines, aircraft, generators, and heavy equipment. Converting to L/h allows comparison with metric-spec machinery. A boat engine consuming 10 US gal/h burns 37.854 L/h — essential for calculating fuel range and costs on international voyages.

🌱 Irrigation & Agriculture

Irrigation system flow rates are frequently specified in US gal/h by American manufacturers, while international agronomists and water authorities use L/h. Converting between the two ensures correct pump sizing, pipe selection, and water usage calculations. A sprinkler rated at 25 US gal/h delivers 94.635 L/h — a critical figure for scheduling irrigation cycles.

🏭 Industrial & Chemical Processes

Chemical plants, refineries, and manufacturing facilities measure liquid flow rates in both gal/h and L/h depending on equipment origin. American equipment specs often use GPH while European systems use L/h. Process engineers regularly convert between units when integrating mixed-origin equipment, calibrating flow meters, or reporting outputs in metric pressure and flow documentation.

🚢 Marine & Aviation

Marine and aviation fuel consumption is traditionally measured in US gallons per hour. Pilots and captains calculating range, endurance, and fuel load for international operations often need to convert GPH to L/h to comply with metric-standard fuel documentation and to purchase fuel at metric-standard refuelling facilities worldwide. A Cessna 172 burns approximately 9 US gal/h ≈ 34 L/h.

🔥 Heating & Boiler Systems

Oil-fired boilers and heating systems in the US specify fuel consumption in US gal/h. Technicians working on imported or exported heating equipment need to convert to L/h for metric-standard maintenance records, efficiency reporting, and fuel cost calculations. A typical oil burner rated at 0.85 US gal/h consumes approximately 3.217 L/h of heating oil.

🏠 Pumps & Water Systems

Home and commercial water pumps sold in the US state flow rates in GPH or GPM, while international plumbing standards use L/h or m³/h. Converting GPH to L/h is needed when sizing scheduled water systems, selecting compatible fittings, or verifying that a US-bought pump meets local water authority requirements. A pool pump at 100 US gal/h ≈ 378.5 L/h.

✅ US vs Imperial Gallon at a Glance: Always confirm which gallon type your equipment uses before converting. A US gal/h figure converted using the Imperial factor will be ~20% too high — a significant error in fuel planning or pump sizing. The US gallon (3.785 L) is used in the USA; the Imperial gallon (4.546 L) is used in the UK and some Commonwealth countries.

Gallons per Hour & Litres per Hour — Key Facts

    📖 Did You Know? The US gallon and the Imperial gallon were once the
    same unit but diverged after American independence. The US gallon is defined as exactly
    231 cubic inches (3.785411784 L), a definition inherited from the old English wine gallon.
    The Imperial gallon was redefined in 1824 as the volume of 10 pounds of water at a
    specific temperature, resulting in the larger 4.54609 litre definition
    still used in the UK today.
  

1 US gallon/h = 3.785411784 litres/h (exact, by international definition)
1 Imperial gallon/h = 4.54609 litres/h (exact, by international definition)
1 litre/h = 0.264172 US gal/h = 0.219969 Imperial gal/h
1 Imperial gal/h = 1.20095 US gal/h — the Imperial gallon is ~20% larger
Flow rate in L/min = L/h ÷ 60; flow rate in m³/h = L/h ÷ 1000
Flow rate in mL/s = L/h ÷ 3.6
GPH (gallons per hour) almost always refers to the US gallon in American contexts
1000 US gal/h = 3,785.41 L/h = 3.785 m³/h
The litre per hour (L/h) is the standard flow unit in ISO and SI metric engineering documentation

⚠️ US vs Imperial — Don't Mix Them Up: Using the wrong gallon conversion factor introduces a ~20% error in every calculation. When reading flow rate specs from equipment manuals or datasheets, always check whether "gallon" refers to the US gallon (common in American documentation) or the Imperial gallon (common in UK/Commonwealth documentation). When in doubt, check the litre equivalent stated in the same document to verify which gallon type is being used.

Frequently Asked Questions — Gallons per Hour to Litres per Hour

How many litres per hour is 1 US gallon per hour?

1 US gallon per hour is exactly 3.785411784 litres per hour. This is the internationally defined conversion factor. So 1 US gal/h = 3.785411784 L/h — no rounding, no approximation. The US gallon is defined as exactly 231 cubic inches, which equals 3.785411784 litres exactly. For a quick estimate, 1 US gal/h ≈ 3.785 L/h.

How many litres per hour is 1 Imperial gallon per hour?

1 Imperial gallon per hour is exactly 4.54609 litres per hour. The Imperial gallon is defined as exactly 4.54609 litres under international agreement. This makes 1 Imperial gal/h = 4.54609 L/h exactly. Note that the Imperial gallon is about 20% larger than the US gallon — so Imperial gal/h values convert to larger L/h figures than the same number in US gal/h.

How do I convert US gallons per hour to litres per hour?

To convert US gallons per hour to litres per hour, multiply the number of US gal/h by 3.785411784. The formula is: L/h = US gal/h × 3.785411784. Examples: 5 US gal/h × 3.785411784 = 18.927 L/h. 10 US gal/h = 37.854 L/h. 100 US gal/h = 378.541 L/h. Use the converter at the top of this page for instant results.

How do I convert litres per hour back to gallons per hour?

To convert litres per hour to US gallons per hour, divide the L/h value by 3.785411784 (or multiply by 0.264172). Formula: US gal/h = L/h ÷ 3.785411784. Examples: 100 L/h ÷ 3.785411784 = 26.417 US gal/h. 500 L/h = 132.086 US gal/h. For Imperial gallons: divide L/h by 4.54609 (or multiply by 0.219969). Example: 100 L/h ÷ 4.54609 = 21.997 Imperial gal/h.

What is the difference between US gallons and Imperial gallons per hour?

The US gallon equals 3.785411784 litres, while the Imperial (UK) gallon equals 4.54609 litres. This means for the same flow rate number: 10 US gal/h = 37.854 L/h, but 10 Imperial gal/h = 45.461 L/h — about 20% more. The Imperial gallon is 1.20095 times larger than the US gallon. Always confirm which gallon type applies to your equipment. US GPH is standard in American documentation; Imperial GPH is standard in British documentation.

How do I convert gallons per hour to litres per minute?

To convert US gallons per hour to litres per minute: first convert to L/h (multiply by 3.785411784), then divide by 60. Or use the direct formula: L/min = US gal/h × 3.785411784 ÷ 60 = US gal/h × 0.063090. Example: 10 US gal/h × 0.063090 = 0.6309 L/min. For Imperial gallons: L/min = Imp gal/h × 4.54609 ÷ 60 = Imp gal/h × 0.075768.

How do I convert gallons per hour to m³ per hour?

To convert US gallons per hour to cubic metres per hour (m³/h): multiply by 3.785411784 to get L/h, then divide by 1000. Or use the direct formula: m³/h = US gal/h × 0.003785411784. Example: 100 US gal/h × 0.003785 = 0.3785 m³/h. 1000 US gal/h = 3.785 m³/h. For Imperial gallons: m³/h = Imp gal/h × 0.00454609. The converter above automatically shows the m³/h equivalent in the result display.

Why does engine fuel consumption use gallons per hour?

Engine fuel consumption is rated in gallons per hour (GPH) in the United States because GPH directly measures how much fuel an engine burns in one hour at a given power setting — regardless of speed or distance. This is more useful than distance-based metrics (like MPG) for stationary engines (generators, pumps, heaters) and for marine/aviation range planning where endurance (hours of operation) is more relevant than distance. International users convert GPH to L/h to match metric fuel standards.

Useful Flow Rate & Unit Conversion Resources

📏 NIST Unit Definitions

The US National Institute of Standards and Technology (NIST) provides official definitions for US customary units including the gallon, with precise metric equivalents used in all scientific and engineering conversions.

NIST Unit Conversions →

🌍 BIPM — SI Units

The International Bureau of Weights and Measures maintains the official SI unit definitions, including the litre and all derived flow rate units used in international engineering and scientific documentation.

BIPM SI Units →

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