Aquarium Calculators & Tools
Free tools for planning, stocking, planting and maintaining your aquarium.
Planning a new aquarium? Start with the Aquarium Planner. The calculators are free to use. Use Save calculation on tools that offer it to find your result again in Saved Calculations.
Aquarium tools
Aquarium Planner
Plan your aquarium, equipment, plants and fish.
Fish Compatibility Checker
Check if fish species can live together.
Fish Stocking Calculator
Check if your planned fish population fits your aquarium.
Aquarium Plant Problem Diagnosis Checker
Explore likely causes of unhealthy aquarium plants.
Aquarium Volume Calculator
Estimate your aquarium's water volume.
Aquarium Stand Calculator
Plan a stand, supports and a lumber cut list.
Aquarium PAR Lighting Calculator
Estimate light intensity at different water depths.
Aquarium Nutrient Solution Calculator
Calculate dry-salt doses and prepare stock solutions.
Aquarium Fertilizer Dosing Calculator
Calculate doses and model nutrient levels over time.
Filter Sizing & Selection Advisor
Assess your filtration setup and compare filter options.
Aquarium Substrate Calculator
Calculate substrate volume and compare package options.
Aquarium Heater Size Calculator
Estimate heater wattage for your aquarium and room.
Aquarium pH/KH/CO2 Calculator
Estimate CO2 from pH and KH; not a direct measurement.
Aquarium Calcium & Magnesium Calculator
Calculate Ca, Mg, water hardness and the Ca:Mg ratio.
Planning guidance
Free Aquarium Calculators for Better Planning
Aquarium calculators can make it easier to plan a freshwater aquarium before choosing equipment, plants, fish or invertebrates. Start with your aquarium volume, then use that information when estimating heater size, fertilizer dosing, substrate requirements or other setup needs.
For planted aquariums, the lighting, fertilizer, substrate and CO₂ tools help you estimate important setup parameters. The Fish Compatibility Checker compares species requirements, while the Aquarium Planner brings several setup decisions together in one guided workflow.
Calculator results are planning estimates rather than fixed rules. Always consider your actual aquarium, fish and invertebrates, plants and equipment, and make changes gradually.