GPM to LPM Converter
Instantly convert US gallons per minute to liters per minute, liters per second, cubic meters per hour, imperial GPM, and more — with live precision control, quick presets for common pump & well flow rates, gallons-per-hour display, and a downloadable PDF report.
Assumes US gallons: 1 US GPM = 3.785411784 LPM, 1 US gal = 3.78541 L, and 1 imperial GPM = 4.54609 LPM (shown separately) — for reference only.
| US GPM | Liters/min | Liters/sec | US gal/hr |
|---|
GPM to LPM Conversion — Complete Guide for 2026
Converting GPM (US gallons per minute) to LPM (liters per minute) is how you compare American water-flow ratings with metric ones. US showerheads, faucets, well pumps, pool pumps, water heaters, and irrigation systems are rated in gallons per minute, while international products, metric pump curves, and most engineering references use liters per minute, liters per second, or cubic meters per hour. The key relationship is exact: 1 US GPM = 3.785411784 LPM, so 1 LPM ≈ 0.264172 US GPM.
Our free GPM to LPM Converter takes a flow rate in US gallons per minute and returns liters per minute, adds a gallons-per-hour reading (10 GPM = 600 gal/hr), and converts across the flow-rate ladder — liters per second, imperial GPM, cubic meters per hour, cubic feet per minute, and cubic meters per day. Quick presets, a log-scale comparison chart, a common-flows reference table, and a downloadable PDF report make it useful for a quick check or for pump, well, and plumbing paperwork.
How to Use the GPM to LPM Converter in 4 Steps
A complete GPM-to-LPM conversion takes a few seconds. Enter a flow rate or tap a preset, choose your precision, and download a PDF report you can attach to a pump quote, well test, or plumbing plan.
Enter the Flow in US GPM
Type any flow rate in US gallons per minute — a fixture rating, a pump curve value, or a well test result. Decimals such as 2.5 or 12.5 GPM are supported, and the result updates on every keystroke.
Or Tap a Quick Preset
Common flows are one tap away: 1, 5, 10, 15, 25, and 50 GPM — from a low-flow fixture to a pool pump. Each chip shows its LPM value, so you can read the answer before you click. The active preset stays highlighted, and typing a matching value re-selects it automatically.
Set Decimal Precision
Use the input or slider to pick 0 to 8 decimal places (the default is 4). One or two decimals are plenty for fixtures, pumps, and wells, whose real flow varies with pressure; more decimals suit engineering and technical records.
Review & Download PDF
See your flow in liters per minute, liters per second, gallons per hour, US GPM, imperial GPM, cubic meters per hour, CFM, and cubic meters per day, plus a chart comparing the numbers. Click Download PDF for a two-page branded report with every conversion, the chart, and a highlighted reference table.
Why 1 US GPM = 3.785411784 LPM
The US gallon descends from the old English wine gallon and is defined as exactly 231 cubic inches. Since the inch was fixed at exactly 2.54 cm, one cubic inch is exactly 16.387064 cm³, and 231 of them make 3,785.411784 cm³ — exactly 3.785411784 liters. The liter itself is one cubic decimeter (1,000 cm³), and 1,000 liters make one cubic meter.
Because both gallons and liters measure volume, the “per minute” part carries straight across: 1 US GPM = 3.785411784 LPM exactly. The reverse factor (0.264172…) is a non-terminating decimal, which is why the calculator multiplies by the exact gallon definition internally rather than using a rounded shortcut.
US gallons vs imperial gallons
“GPM” can mean two different gallons, and the difference is large enough to matter:
- US gallon — 231 in³ = 3.785411784 L. Used on all US fixtures, pumps, and appliances.
- Imperial (UK) gallon — 4.54609 L, about 20% larger. Found on older UK and some Canadian equipment and specifications.
- Converting between them — 1 US GPM ≈ 0.8327 imperial GPM, and 1 imperial GPM ≈ 1.2010 US GPM.
On a 10 GPM well pump, mixing up the two gallons changes the metric result by about 7.6 LPM (37.85 vs 45.46 LPM). Because the conversion itself is exact, the only real uncertainty in your result is the flow rate you start with — and real-world flow depends on water pressure, pipe size, and how the measurement was taken.
What the GPM to LPM Converter Calculates
More than a single LPM figure — the tool gives you a complete flow-rate breakdown across metric, US, and imperial units, formatted for fixtures, pumps, wells, pools, irrigation, or reports.
Liters per Minute (Hero Result)
The headline result multiplies your US GPM by exactly 3.785411784, with a summary line beneath it that also gives liters per second and gallons per hour — the unit on most metric fixtures, pumps, and product sheets.
Liters per Second
Liters per second (LPM ÷ 60) are the standard in engineering, irrigation design, and water-supply specifications in many countries. Having L/s next to LPM lets you match a design document without a second calculation.
US Gallons per Hour
Gallons per hour (GPM × 60) is how small pumps, pond and fountain pumps, drip irrigation, and water treatment systems are often rated. 10 GPM is 600 gal/hr, so you can compare a GPM rating with a GPH one at a glance.
Cubic Meters per Hour & per Day
Cubic meters per hour (LPM × 0.06) appear on metric pump curves and pool equipment, while cubic meters per day suit well yields, water treatment, and daily household demand in metric terms.
Imperial GPM & CFM
Imperial gallons per minute (LPM ÷ 4.54609) cover older UK and Canadian specs, and cubic feet per minute (LPM ÷ 28.3168) express water flow in cubic feet for engineering calculations — not to be confused with air-flow CFM.
Chart, Reference Table & PDF
A log-scale bar chart compares your value in GPM, LPM, gal/hr, L/s, and m³/hr so very different magnitudes fit on one view. A reference table of common flows highlights your input when it matches, and the two-page PDF bundles everything for sharing or record-keeping.
GPM to LPM Conversion Chart — Common Values
Bookmark this page or screenshot the table below for instant reference. Every value uses the exact definition 1 US gallon = 3.785411784 L, rounded to four decimals. Fixture limits reflect US federal and WaterSense figures; pump, well, and pool examples are typical ranges that vary by product and pressure.
| US GPM | Liters/Min | Liters/Sec | m³/Hour | Common Use |
|---|---|---|---|---|
| 1 GPM | 3.7854 LPM | 0.0631 L/s | 0.2271 m³/h | Low-flow bathroom faucet |
| 1.5 GPM | 5.6781 LPM | 0.0946 L/s | 0.3407 m³/h | WaterSense bathroom faucet (max) |
| 2 GPM | 7.5708 LPM | 0.1262 L/s | 0.4542 m³/h | WaterSense showerhead (max) |
| 2.2 GPM | 8.3279 LPM | 0.1388 L/s | 0.4997 m³/h | US federal faucet limit |
| 2.5 GPM | 9.4635 LPM | 0.1577 L/s | 0.5678 m³/h | US federal showerhead limit |
| 5 GPM | 18.9271 LPM | 0.3155 L/s | 1.1356 m³/h | Garden hose (typical) |
| 8 GPM | 30.2833 LPM | 0.5047 L/s | 1.8170 m³/h | Small household well pump |
| 10 GPM | 37.8541 LPM | 0.6309 L/s | 2.2712 m³/h | Typical household well pump |
| 12 GPM | 45.4249 LPM | 0.7571 L/s | 2.7255 m³/h | Peak demand, larger home (typical) |
| 15 GPM | 56.7812 LPM | 0.9464 L/s | 3.4069 m³/h | Irrigation zone or larger well pump |
| 20 GPM | 75.7082 LPM | 1.2618 L/s | 4.5425 m³/h | Multi-zone irrigation or large home |
| 25 GPM | 94.6353 LPM | 1.5773 L/s | 5.6781 m³/h | Small pool or spa pump |
| 50 GPM | 189.2706 LPM | 3.1545 L/s | 11.3562 m³/h | Residential pool pump (typical) |
| 100 GPM | 378.5412 LPM | 6.3090 L/s | 22.7125 m³/h | Commercial or agricultural pump |
How to Use GPM and LPM for Pumps, Wells, and Pools
The most common reasons people convert GPM to LPM are to compare a US pump or fixture with a metric one, to read a metric pump curve, and to size flow for a pool, well, or irrigation system. Each one needs the unit conversion — and an understanding that flow rate depends on pressure, so a rating is only valid under the conditions it was measured at.
The manual calculation
Step 1: Work out the flow you need in US GPM. Step 2: Multiply by 3.785411784 for LPM. Step 3: Multiply LPM by 0.06 for cubic meters per hour, the unit on many metric pump curves. For a 20,000-gallon pool that should turn over once every 8 hours:
41.67 GPM × 3.785411784 = 157.73 LPM
157.73 LPM × 0.06 = 9.46 m³/h (2,500 gal/hr)
Result: a pump delivering about 9.5 m³/h at your system’s head
Enter the GPM figure into the calculator and it does the rest: the hero result shows LPM, the cubic-meters-per-hour line matches a metric pump curve, and the gallons-per-hour reading matches US pool and pond pumps. Choose a pump whose curve delivers that flow at your system’s actual resistance, not just its maximum open-flow rating.
Measuring your own flow rate
To check a faucet, hose, or well supply yourself, use a simple bucket test:
- Time the fill — open the tap fully and time how long a bucket of known size takes to fill.
- Calculate GPM — gallons ÷ seconds × 60. A 5-gallon bucket filled in 30 seconds is 10 GPM.
- Convert — enter the result above: 10 GPM = 37.85 LPM, or about 0.63 L/s.
- Repeat — measure two or three times and average, and test well supplies over a longer period to see whether flow holds up.
GPM to LPM — Key Conversion Numbers
The GPM to LPM Converter Is Built For You If…
Whether you’re checking a home’s well, choosing a showerhead, or sizing a pool pump — this calculator gives you the exact answer in seconds, with a report you can save and share.
Homeowners & Homebuyers
Fixtures, wells & water useUS fixtures and well tests are reported in GPM, while imported fixtures, international product listings, and many online tools use LPM. Converting helps you compare showerheads and faucets, understand a well flow test during a home purchase, and estimate water use.
- A 2.5 GPM showerhead is about 9.46 LPM
- Ask for the well’s sustained yield, not just pump GPM
- Use a bucket test to check real fixture flow
- Lower-flow fixtures cut both water and water-heating costs
Plumbers, Well & Irrigation Pros
Pumps, pipes & zonesContractors move between US GPM ratings, metric pump curves in m³/h or L/min, irrigation designs in L/s, and occasional imperial specs. An exact converter with a printable report keeps quotes, pump selections, and zone designs consistent.
- 1 GPM = 0.2271 m³/h for metric pump curves
- 1 L/s ≈ 15.85 GPM for irrigation designs
- Confirm US vs imperial gallons on older specs
- Attach the PDF to show the factor used
Pool, Spa & Pond Owners
Pumps, filters & turnoverPool and pond equipment is rated in GPM, gallons per hour, or cubic meters per hour depending on the brand. Converting helps you match a pump to a filter’s maximum flow, check turnover time, and compare equipment from different manufacturers.
- Turnover GPM = pool gallons ÷ (hours × 60)
- Keep pump flow below the filter’s rated maximum
- Compare pumps at the same head, not open flow
- Fill time (minutes) = pool gallons ÷ hose GPM
7 Tips for Accurate GPM to LPM Conversions
The conversion is exact, but flow ratings around it are easy to misread. Most mistakes come from mixing US and imperial gallons, ignoring pressure, confusing time units, and rounding the factor too far. These rules keep every conversion trustworthy.
Confirm US or Imperial Gallons
A US gallon is 3.785 L; an imperial gallon is 4.546 L. US products use US gallons, but older UK and Canadian equipment may not. If a spec just says “GPM,” check the country of origin before converting.
Flow Depends on Pressure
Fixture limits are rated at a specific pressure, and pump flow drops as head rises. Convert the flow at your actual operating conditions, and compare products at the same pressure or head.
Match the Time Unit
Flow can be per second, minute, hour, or day. 1 GPM = 60 gal/hr = 1,440 gal/day, and 1 LPM = 60 L/hr. Convert gallons to liters first, then adjust the time unit — or let the calculator show them all at once.
Don’t Round to 4
Multiplying by 4 overstates LPM by about 5.7%, and 3.8 by about 0.4%. Use 3.785 for everyday work and the exact 3.785411784 for engineering and specifications — the calculator uses the exact figure.
Well Yield vs Pump Rate
A pump can draw faster than a well refills. For a home purchase or new system, ask for the sustained yield from a timed well flow test, and convert that figure — not the pump’s nameplate rating.
Measure, Don’t Assume
Aerators clog, pressure varies, and older fixtures may exceed their labels. A quick bucket test — gallons ÷ seconds × 60 — gives your real GPM to convert, which is far more useful than a label value.
Memorize Three Anchors for Mental Math
1 GPM ≈ 3.8 LPM. 10 LPM ≈ 2.6 GPM. 1 m³/h ≈ 4.4 GPM. With these you can sanity-check any spec in your head — a 2.5 GPM showerhead is about 9.5 LPM, and a 12 LPM tap is about 3.2 GPM.
GPM to LPM Converter — Frequently Asked Questions
Everything you need to know about converting gallons per minute to liters per minute, US vs imperial gallons, and how to apply this calculator to fixtures, wells, pumps, pools, and irrigation.
One US gallon per minute equals exactly 3.785411784 liters per minute, or about 3.785 LPM. The figure is exact because the US gallon is defined as 231 cubic inches, and the inch is exactly 2.54 cm, so one US gallon is exactly 3.785411784 liters.
Multiply US gallons per minute by 3.785411784: LPM = GPM × 3.785411784. For example, 5 GPM = 18.93 LPM, 10 GPM = 37.85 LPM, and 25 GPM = 94.64 LPM. To go from LPM back to GPM, divide by 3.785411784, or multiply by about 0.264172.
Multiply liters per minute by about 0.264172 (the same as dividing by 3.785411784). For example: 10 LPM = 2.6417 GPM, 20 LPM = 5.2834 GPM, 50 LPM = 13.2086 GPM, and 100 LPM = 26.4172 GPM. This converter takes US GPM as its input; to check a result, enter the GPM figure you calculated and confirm the LPM result matches.
A US gallon is 3.785411784 liters, while an imperial (UK) gallon is 4.54609 liters — about 20% larger. So 1 imperial GPM equals 4.54609 LPM, or about 1.20095 US GPM, and 1 US GPM equals about 0.83267 imperial GPM. US products use US gallons; older UK and some Canadian equipment may use imperial gallons, so check which one a spec means before converting.
Under US federal standards, showerheads are limited to 2.5 GPM (9.46 LPM) and kitchen and bathroom faucets to 2.2 GPM (8.33 LPM). WaterSense-labeled showerheads use 2.0 GPM (7.57 LPM) or less, and WaterSense bathroom faucets use 1.5 GPM (5.68 LPM) or less. Some states set lower limits, so check local codes before buying fixtures.
A sustained well yield of about 5 GPM (about 18.9 LPM) or more is often cited as adequate for a typical household, and many home well pumps are sized for roughly 8 to 12 GPM (about 30 to 45 LPM). Requirements vary by lender, local health department, and household size, and a well’s sustained yield can be lower than its pump’s rated flow, so rely on a proper well flow test when buying a home.
Use a bucket test. Time how many seconds it takes to fill a bucket of known size with the tap or hose fully open, then divide the bucket’s gallons by the seconds and multiply by 60. A 5-gallon bucket that fills in 30 seconds means 5 ÷ 30 × 60 = 10 GPM, or about 37.85 LPM.
Divide the pool’s volume in gallons by the flow rate in GPM to get minutes. A 20,000-gallon pool filled by a garden hose at 5 GPM takes 20,000 ÷ 5 = 4,000 minutes, or about 66.7 hours. In metric terms, that pool holds about 75,708 liters, and 5 GPM is about 18.93 LPM — the same answer either way.
One US GPM equals about 0.2271 cubic meters per hour and 0.0631 liters per second. Going the other way, 1 m³/h equals about 4.4029 GPM, and 1 L/s equals about 15.8503 GPM. Cubic meters per hour are common on metric pump curves, and liters per second are common in engineering and irrigation specifications.
One GPM is exactly 60 gallons per hour and 1,440 gallons per day. In metric terms, 1 US GPM is about 227.12 liters per hour and 5.451 cubic meters per day. Small pumps, drip irrigation, and water treatment equipment are often rated in gallons per hour or per day.
One cubic foot holds about 7.48052 US gallons, so 1 GPM equals about 0.13368 cubic feet per minute (CFM) of water. CFM is usually used for air flow in ventilation and HVAC, so this liquid-volume figure should not be compared with fan or blower CFM ratings.
The converter uses exact definitions: 1 US gallon = 3.785411784 L; 1 imperial gallon = 4.54609 L; 1 cubic foot = 28.316846592 L; and 1 m³ = 1,000 L. Calculations use double-precision floating-point arithmetic, accurate to about 15 significant digits. In practice, accuracy is limited by how the flow was measured and by water pressure, not by the conversion.
Accuracy note: The HomeExpertly GPM to LPM Converter uses the exact definitions 1 US gallon = 231 cubic inches = 3.785411784 liters, so 1 US GPM = 3.785411784 LPM, together with 1 imperial gallon = 4.54609 liters, 1 cubic foot = 28.316846592 liters, and 1 cubic meter = 1,000 liters, based on the inch as defined by the 1959 International Yard and Pound Agreement and recognized by the U.S. National Institute of Standards and Technology (NIST). All calculations are mathematically precise to the precision displayed. However, results are for informational and reference purposes only. Real-world flow depends on water pressure, pump head, pipe size, and measurement method, and a well’s sustained yield can differ from a pump’s rated flow. Fixture limits, well guidelines, and pump and pool examples on this page are typical or regulatory figures that vary by product, jurisdiction, and date, and regulations can change. For applications where flow is critical — including but not limited to well testing for property transactions, pump and filter selection, irrigation design, plumbing code compliance, fire protection, or contract pricing — always verify figures independently using manufacturer specifications, a certified flow test, current local codes, and a licensed plumber, well contractor, or other qualified professional. HomeExpertly is not responsible for any consequences arising from the use of these conversions, including but not limited to inadequate water supply, undersized or oversized equipment, code violations, or equipment damage.