Aquarium Evaporation Rate Calculator

Why Water Evaporation Happens in Fish Tanks

Evaporation happens when heat from lights or the room warms the tank water and causes it to turn into vapor. The lower the humidity, the faster this happens.

Tanks with open tops or strong lighting systems lose more water. Over time, this can stress your fish, change water chemistry, or lower the waterline dangerously if you don’t top it off.

Calculate How Much Water Your Aquarium Loses Daily

If your tank water level keeps going down and there’s no leak, it’s probably just evaporation. It happens more than most people think—especially in open-top tanks or warm rooms.

This free aquarium evaporation calculator lets you figure out how much water your tank loses every day or week. Just type in your tank size, room temperature, humidity level, and how long your lights stay on. You’ll get a good estimate in liters.

The tool works whether you measure in Fahrenheit or Celsius. It also adjusts based on how much your tank is covered.

By knowing your evaporation rate, you can plan your water top-offs better and keep your fish safe from sudden water level changes. It’s simple, fast, and designed for everyday aquarium owners.

Free Aquarium Evaporation Calculator (Liters)

If you’re losing water from your fish tank and can’t figure out why, you’re not alone. Aquarium water evaporation is a common issue for fishkeepers—especially in warm, dry rooms or with open-top tanks.

Use this Aquarium Evaporation Calculator to estimate how many liters of water your tank loses every day and every week. It’s perfect for freshwater and saltwater tanks, turtle enclosures, and even planted aquariums.

What This Calculator Does

This tool gives a realistic estimate of your daily and weekly water loss, based on your tank’s surface area and environmental conditions. It’s great for beginners and experienced aquarists alike who want to:

• Avoid over- or under-topping
• Plan for auto top-off systems
• Maintain stable water parameters
• Reduce stress on aquatic pets

How the Aquarium Evaporation Calculator Works

You’ll enter:

• Tank dimensions – Length and width in inches
• Room temperature – In °F or °C (both are supported)
• Humidity level – Based on your local reading or a digital hygrometer
• Lid type – Open top, partially covered, or fully covered
• Lighting duration – Number of hours your lights stay on each day

The tool calculates the tank’s surface area, then estimates evaporation based on temperature, humidity, lighting, and how open the tank is.

The result? An estimate of how many liters evaporate per day and per week.

Don’t Know Your Humidity Level?

You can check humidity easily with:

• A cheap digital hygrometer
• A weather app like AccuWeather or your phone’s built-in weather tool
• Smart home devices like Alexa or Google Nest that show humidity

Even a rough guess is better than leaving it blank.

Who Should Use This Tool?

This tool is useful for:

• Aquarium hobbyists managing freshwater or marine tanks
• Turtle or amphibian keepers with basking areas
• Paludarium owners trying to balance water and air zones
• Anyone planning an auto top-off system

Avoid Problems Caused by Evaporation

• Saltwater tanks can experience salinity spikes
• Shrimp and sensitive fish can suffer from water parameter changes
• Evaporation may expose heaters or filters, leading to damage

By using this calculator, you stay ahead of these issues and protect your aquarium’s health.