A trash can volume calculator determines the capacity of cylindrical or tapered waste bins. Enter dimensions to find volume in gallons and liters, and match it to the right bag size.
Trash can volume is the capacity of a waste bin, typically measured in gallons or liters. Trash cans come in sizes from 2 gallons (small bathroom) to 96 gallons (curbside rollout). Most are cylindrical or frustum-shaped (wider at top).
Knowing your trash can volume helps you buy the right size trash bags and estimate waste disposal needs.
Cylindrical can: V = π × (diameter/2)² × height.
Tapered can: V = (πh/3)(r₁² + r₂² + r₁r₂).
Example: Round can 36 cm diameter, 45 cm tall:
V = π × 18² × 45 = 45,804 cm³ = 45.8 L ≈ 12.1 US gallons.
D 20 cm, H 28 cm: V = π×10²×28 = 8,796 cm³ = 8.8 L ≈ 2.3 gal.
D 36 cm, H 62 cm: V = π×18²×62 = 63,088 cm³ = 63.1 L ≈ 16.7 gal.
D 30 cm, H 40 cm: V = π×15²×40 = 28,274 cm³ = 28.3 L ≈ 7.5 gal.
D 56 cm, H 106 cm: V = π×28²×106 = 261,101 cm³ = 261 L ≈ 69 gal.
35 free volume calculation tools — click any calculator to get started.
Answers to common questions about the trash can volume calculator.
Match bag gallon rating to can size. 4 gal bags for bathroom bins. 13 gal bags for kitchen cans. 33 gal bags for large indoor bins. 55-65 gal bags for outdoor cans. Always buy bags slightly larger than the can for overhang.
Bathroom: 2-4 gal. Office: 7-10 gal. Kitchen step-on: 10-13 gal. Tall kitchen: 13-16 gal. Outdoor: 32-96 gal. Commercial: 44-55 gal.
If you change bags twice a week: ~104 bags/year for kitchen. Once a week for bathroom: ~52 bags/year. Buy boxes of 50-100 for best value.
Measure both the top diameter and bottom diameter, plus height. Use the frustum formula: V = (πh/3)(r₁² + r₂² + r₁r₂). The tapered shape makes the actual volume less than a pure cylinder.
Average US household: 18 lbs (8.2 kg) of trash per week ≈ 2-3 trash bags of 13 gallons each. That's about 30-40 gallons of waste per week.