June 8, 2026 Aquarium Heater Size Calculator US Units (gal, °F, in) Metric (L, °C, cm) Enter Volume Calculate from Dimensions Aquarium Volume Length Width Height Computed Volume Target Temp Room Temp Tank Cover Covered (glass lid / canopy) Partially covered Open top Safety Margin (%) 20% Operating Cost Estimate Electricity Rate ($/kWh) Heater Duty Cycle (%) 50% Calculate Reset Copy Result Download PDF Recommended: — Base heating need: — With safety margin: — Watts per gal: — Daily cost: — Monthly cost: —