That's a great and practical question! The average capacity for a standard outdoor trash can you see on a city sidewalk is typically between 30 to 45 gallons (approximately 115 to 170 liters). You'll most commonly find 32-gallon and 44-gallon models. These are the workhorses of urban waste collection, designed to be large enough to handle daily pedestrian traffic but not so large that they become impossible for sanitation workers to empty efficiently.
The specific size can vary based on the city's budget, the expected foot traffic in an area, and the frequency of collection. In very high-traffic zones like tourist districts or transit hubs, you might see larger barrels, sometimes up to 55 gallons. The classic "litter basket" on a pole holds much less, usually around 20 gallons. These standard cans are often made from durable, weather-resistant materials like galvanized steel, heavy-duty plastic, or concrete. So, next time you're walking down the street, you can confidently estimate that the standard green or black barrel is holding roughly 30-45 gallons of waste, a key detail in keeping our public spaces clean.