Gallon Calculator & Converter
Convert gallons instantly with our free gallon calculator. Convert between US gallons, UK/Imperial gallons, liters, quarts, pints, cups, and fluid ounces. Perfect for cooking, fuel economy, pools, aquariums, tanks and liquid measurements. Key conversions: 1 US gallon = 3.785 liters | 1 UK gallon = 4.546 liters | 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fl oz.
Quick Gallon Conversions
Master these essential gallon conversion formulas for cooking, fuel, and liquid measurements:
UK/Imperial Gallon: 1 UK gal = 4.546 liters = 4 quarts = 8 pints = 160 fl oz
UK vs US: 1 UK gallon = 1.201 US gallons (UK gallons are larger)
💡 Quick Conversions
💡 Common Sizes
💡 Recipe Conversions
💡 Common Scenarios
📊 Gallon Conversion Tables
US Gallons to Other Units
| US Gallons | Liters | UK Gallons | Quarts | Pints | Cups | Fluid Oz |
|---|---|---|---|---|---|---|
| 0.5 gal | 1.89 | 0.42 | 2 | 4 | 8 | 64 |
| 1 gal | 3.79 | 0.83 | 4 | 8 | 16 | 128 |
| 2 gal | 7.57 | 1.67 | 8 | 16 | 32 | 256 |
| 5 gal | 18.93 | 4.16 | 20 | 40 | 80 | 640 |
| 10 gal | 37.85 | 8.33 | 40 | 80 | 160 | 1,280 |
| 20 gal | 75.71 | 16.65 | 80 | 160 | 320 | 2,560 |
| 50 gal | 189.27 | 41.63 | 200 | 400 | 800 | 6,400 |
| 100 gal | 378.54 | 83.27 | 400 | 800 | 1,600 | 12,800 |
Liters to Gallons
| Liters | US Gallons | UK Gallons | Quarts (US) | Pints (US) | Fluid Oz (US) |
|---|---|---|---|---|---|
| 1 L | 0.264 | 0.220 | 1.057 | 2.113 | 33.81 |
| 2 L | 0.528 | 0.440 | 2.113 | 4.227 | 67.63 |
| 5 L | 1.321 | 1.100 | 5.283 | 10.567 | 169.07 |
| 10 L | 2.642 | 2.200 | 10.567 | 21.134 | 338.14 |
| 20 L | 5.283 | 4.399 | 21.134 | 42.268 | 676.28 |
| 50 L | 13.209 | 10.998 | 52.834 | 105.669 | 1,690.70 |
📐 Common Gallon Calculations
US Liquid Measures
- 1 Gallon = 4 Quarts
- 1 Gallon = 8 Pints
- 1 Gallon = 16 Cups
- 1 Gallon = 128 Fluid Ounces
- 1 Gallon = 256 Tablespoons
- 1 Gallon = 768 Teaspoons
Metric Conversions
- 1 US Gallon = 3.785 Liters
- 1 US Gallon = 3,785 mL
- 1 UK Gallon = 4.546 Liters
- 1 UK Gallon = 4,546 mL
- 1 Liter = 0.264 US Gallons
- 1 Liter = 0.220 UK Gallons
Pool & Tank Volumes
- 1 Cubic Foot = 7.481 US Gallons
- 1 Cubic Meter = 264.17 US Gallons
- 10 Gal Aquarium ≈ 40×20×20 cm
- 55 Gal Aquarium ≈ 48×12×21 in
- Small Pool (12×24) ≈ 5,000 gal
- Average Pool ≈ 15,000-20,000 gal
Gallon Formulas & Conversion Factors
Essential formulas for gallon conversions and volume calculations:
• Cubic Feet to US Gallons: ft³ × 7.48052
• Cubic Inches to US Gallons: in³ ÷ 231
• Cubic Meters to US Gallons: m³ × 264.172
• Liters to US Gallons: L × 0.264172
Tank Volume (Rectangular):
• Volume (gal) = L × W × H (in feet) × 7.48052
• Volume (gal) = L × W × H (in inches) ÷ 231
Fuel Economy:
• MPG = Distance (miles) ÷ Fuel (gallons)
• L/100km = 235.215 ÷ MPG (US)
• km/L = MPG (US) × 0.425144
Pro Tip: Remember that UK/Imperial gallons are larger than US gallons (1 UK gal = 1.201 US gal)
🔍 People Also Ask About Gallons
How many liters are in a gallon?
1 US gallon = 3.78541 liters. For UK/Imperial gallons, 1 UK gallon = 4.54609 liters. This is why fuel prices look different between the US and UK - UK gallons are about 20% larger than US gallons.
How many cups are in a gallon?
There are 16 cups in a US gallon. This breaks down as: 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces. In UK measurements, there are 16 imperial cups in an imperial gallon.
How many quarts are in a gallon?
There are 4 quarts in a gallon, both for US and UK measurements. Each quart contains 2 pints or 4 cups. This relationship is consistent in both measurement systems.
How many pints are in a gallon?
There are 8 pints in a gallon. Since 1 quart = 2 pints and 1 gallon = 4 quarts, then 1 gallon = 8 pints. This applies to both US and Imperial measurements.
What's the difference between US and UK gallons?
A UK (Imperial) gallon is larger than a US gallon. 1 UK gallon = 4.546 liters, while 1 US gallon = 3.785 liters. This means 1 UK gallon = 1.201 US gallons, or about 20% more volume.
How many fluid ounces are in a gallon?
128 fluid ounces in a US gallon. For UK gallons, there are 160 Imperial fluid ounces (UK fl oz are smaller than US fl oz). In cooking, this means 1 cup = 8 fl oz, so 16 cups × 8 = 128 fl oz.
How do I calculate gallons in a pool?
Rectangular pool: Length × Width × Average Depth × 7.48 (all in feet) = gallons. For a 20×40 foot pool with 5ft average depth: 20 × 40 × 5 × 7.48 = 29,920 gallons. Round/oval pools use different formulas.
How many gallons in an aquarium?
Tank volume: L × W × H (inches) ÷ 231 = gallons. Common sizes: 10 gallon (20×10×12"), 20 gallon (24×12×16"), 55 gallon (48×13×21"), 75 gallon (48×18×21"), 125 gallon (72×18×21").
How many gallons of gas does a car hold?
Most cars hold 12-16 gallons, compact cars 9-12 gallons, and SUVs/trucks 20-30+ gallons. Check your owner's manual for exact capacity. At 30 MPG with a 15 gallon tank, you can travel about 450 miles.
How do I convert gallons to liters?
Multiply US gallons by 3.78541 to get liters. For example, 5 US gallons × 3.78541 = 18.93 liters. For UK gallons, multiply by 4.54609. To convert liters to US gallons, divide by 3.78541.
How much does a gallon of water weigh?
1 US gallon of water weighs about 8.34 pounds (3.78 kg) at room temperature. A UK gallon of water weighs about 10 pounds (4.54 kg). This varies slightly with temperature - cold water is denser.
What is MPG and how is it calculated?
MPG (Miles Per Gallon) = Distance traveled ÷ Fuel used. If you drove 300 miles on 10 gallons: 300 ÷ 10 = 30 MPG. The US average is about 25 MPG. Hybrids get 40-60 MPG, trucks get 15-20 MPG.
👥 Who Uses Gallon Calculators?
Cooking & Baking
Convert between cups, pints, quarts, and gallons for recipes. Scale recipes up or down and convert between US and metric measurements.
Fuel & Driving
Calculate fuel economy (MPG), trip fuel costs, and compare fuel efficiency. Essential for road trips, fleet management, and budgeting.
Pool & Hot Tub
Calculate water volume for chemical treatments, heating costs, water bills, and filling time estimates for pools and spas.
Aquarium & Fish Tanks
Determine tank volume for stocking fish, calculating filter size, heater wattage, and medication dosing for aquariums.
Home & Garden
Calculate water tank capacity, irrigation needs, paint coverage, and liquid storage for home improvement projects.
Industrial & Commercial
Measure liquid inventory, tank capacity, chemical mixing ratios, and process volumes for manufacturing and business.
❓ Frequently Asked Questions
A gallon is a unit of volume used primarily in the United States (US gallon = 3.785 liters) and the United Kingdom (Imperial gallon = 4.546 liters). It's commonly used for measuring liquids like fuel, milk, and water. The US gallon is defined as 231 cubic inches.
The US and UK gallons have different historical definitions. The US gallon is based on the Queen Anne wine gallon (231 cubic inches), while the Imperial gallon was defined in 1824 as the volume of 10 pounds of water. This resulted in the UK gallon being about 20% larger than the US gallon.
Our calculator uses exact mathematical conversion factors and is accurate to multiple decimal places. Results are rounded for readability but internally use precise values like 3.78541178 liters per US gallon. Accuracy depends on the precision of your input measurements.
For rectangular pools: multiply Length × Width × Average Depth (all in feet), then multiply by 7.48 to get gallons. For round pools: π × radius² × average depth × 7.48. For oval pools: 0.89 × length × width × average depth × 7.48. Our tank calculator handles these calculations automatically.
MPG (Miles Per Gallon) = Distance traveled (miles) ÷ Fuel used (gallons). To track your vehicle's MPG: fill your tank, reset your trip odometer, drive normally, then divide miles traveled by gallons needed to refill. The EPA rates new cars, but real-world MPG varies with driving conditions.
Use these US cooking conversions: 1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces = 256 tablespoons = 768 teaspoons. For metric: 1 cup ≈ 240 mL, 1 tablespoon = 15 mL, 1 teaspoon = 5 mL. Our cooking tab makes these conversions instant.
The general rule is 1 inch of fish per gallon, but this varies by species. Small tropical fish: about 1 inch per gallon. Larger fish need more space. Goldfish need 20+ gallons for the first fish. Always research specific species requirements and consider filtration capacity.
To convert US MPG to L/100km: divide 235.215 by the MPG value. For example, 30 MPG = 235.215 ÷ 30 = 7.84 L/100km. For UK MPG to L/100km: divide 282.481 by the MPG value. Lower L/100km means better fuel efficiency.
Calculator verified for accuracy by measurement standards professionals and engineers.
Last verified: February 15, 2026 • Conversions verified against NIST standards