Aquarium Chiller Sizing Calculator

About this calculator

Aquarium chiller sizing calculates the cooling capacity in BTU/hr needed to lower and hold a tank's water temperature by a specific number of degrees, based on the tank's water volume, the desired temperature drop, and how quickly the chiller needs to achieve it. Larger volumes and bigger temperature drops both require proportionally more cooling capacity, and ambient room temperature and tank insulation also factor in because heat constantly migrates back into the tank from the surrounding air.

Reef keepers and tropical/coldwater fish keepers size a chiller carefully because many sensitive species — particularly corals and coldwater fish like goldfish or certain trout — suffer stress or death outside a narrow temperature band, and an undersized chiller can run constantly without ever reaching the target temperature during hot weather, while lighting and pump equipment in the tank add heat load that must be factored into the sizing as well.

This calculator takes your tank volume and the temperature drop you need and returns the BTU/hr chiller capacity to look for when buying equipment.