Aquarium Water Volume Calculator | Actual Volume, Substrate Amount, Weight, Heater Wattage & Salt Bath
Just enter the outer dimensions of your tank and get the actual water volume, not the catalog figure, after subtracting glass thickness, the water level drop, substrate, and rocks or driftwood. It also shows the amount of oiso sand, river sand, coral sand or soil you need (kg, L, number of bags), the total weight of water, substrate and glass with the load per square meter of floor, the heater wattage to choose from your winter room temperature, a guideline for filter flow rate, water change volume and dechlorinator dose, grams of salt for a 0.5% salt bath (with teaspoon and tablespoon conversion), and a guideline for how many medaka, goldfish or small tropical fish you can keep, all on one screen.
1. Tank size
Choose a standard size or enter the outer dimensions (width x depth x height). The glass thickness is written in the tank's manual or on the packaging.
2. Substrate & layout
From the substrate type and thickness, this gives the amount needed (kg, L, number of bags) and how much water volume the substrate takes up.
Rocks, driftwood & plants
Actual water volume
About 51.5L
After subtracting glass, water level drop, substrate and layout
Catalog volume (outer size)
64.8L
Inner size 59x29x35.5cm
Amount of Oiso sand
11kg
6.8 L / 3 bags if 5 kg per bag
Total weight (water + substrate + glass)
About 73kg
About 404 kg per 1 m2 of base, stand and equipment not included
Heater wattage
Choose based on the lowest winter room temperature and the water temperature you want to keep.
Required wattage
52W
Heater to choose
80W
The guideline is "about 1 W per liter of water when the room and water temperatures differ by 10 C". If the wattage is too low, the water will not reach the target temperature in midwinter. If in doubt, go one size up and set the temperature with a thermostat.
Filter flow rate
A flow rate that circulates the tank water 5 to 10 times per hour is the guideline.
Per hour
258 to 515L/h
Per minute
4.3 to 8.6L/min
The flow rate printed on the filter box is the maximum with no hoses or filter media. In practice it drops by 20 to 30%, so choosing the middle to upper part of the range above is safer. Use more for planted tanks and goldfish, and weaker flow for bettas and fry.
Water change & dechlorinator amount
For the dechlorinator dose, enter the "x mL per x L of water" from the label of your product.
30% water change
15.5L
2 buckets of 10 L
Dechlorinator
1.55mL
For initial setup (full volume): 5.2 mL
Salt amount for salt bath
Calculated with table salt (refined salt). Coarse salt is lighter, about 5 g per teaspoon.
Salt for 0.5%
257.5g
About 42.9 teaspoons / 14.3 tablespoons
Per portion if split into 3
85.8g
77.3 g for 15.5 L of new water at a water change
In a tank with plants, shrimp, snails, corydoras or other animals sensitive to salt, do the salt bath in a separate container. Do not add the salt all at once; dissolve it in portions several hours apart.
Stocking guideline
Based on commonly used rules of thumb and calculated from the actual water volume.
Stocking guideline
17 fish max
Guideline: 1 L of water per 1 cm of body length
The stronger the filtration and the more frequent the water changes, the more headroom you have, and right after setup (about the first month) it is safer to start with half the guideline or less. This does not apply to territorial fish or fish that grow large.
ABOUT
About Aquarium Water Volume Calculator | Actual Volume, Substrate Amount, Weight, Heater Wattage & Salt Bath
The Aquarium Water Volume Calculator works out the "actual water volume" from the tank size, together with the amounts of supplies that follow from it. The volume printed in catalogs is often just outer width x depth x height, but the real volume is smaller because of the glass thickness, the water level kept below the rim, the substrate, and rocks or driftwood. For example, a standard 60cm tank (60x30x36cm, 5mm glass) is about 65 L in the catalog, but with the water level lowered 3cm and 4cm of oiso sand, it actually holds about 52 L. Based on that actual volume, this tool calculates the amount of substrate (kg, L, number of bags), the total weight of water, substrate and glass with the load per square meter of floor, the heater wattage chosen from the winter room temperature and the water temperature you want to keep, a guideline for filter flow rate, the water change volume and dechlorinator dose, the grams of salt for a 0.3% to 0.6% salt bath (with teaspoon and tablespoon conversion), and a guideline for how many medaka, goldfish, small tropical fish and shrimp you can keep.
How to use Aquarium Water Volume Calculator | Actual Volume, Substrate Amount, Weight, Heater Wattage & Salt Bath
- 1Choose a standard size such as "60cm standard", "45cm standard" or "30cm cube", or enter the outer dimensions (width, depth, height) and the glass thickness of your tank
- 2Enter how many cm below the rim the water surface sits (usually 2 to 3 cm)
- 3Choose the substrate type (oiso sand, river sand, silica sand, coral sand, soil, or none), its thickness, and how much space rocks, driftwood and plants take up
- 4Check the "actual water volume", the "substrate amount and number of bags" and the "total weight"
- 5As needed, enter numbers in the sections for heater, filtration, water change and dechlorinator, salt bath, and stocking guideline
- 6Use "Copy all results" to save the results as text for a shopping list or when asking for advice
Great for
- You want to know the correct water volume to work out how many mL of dechlorinator or medication to add to a 60cm tank
- You are setting up a tank and want to know how many bags of oiso sand or soil to buy
- You want to check whether the floor can take a 90cm or 120cm tank in a second-floor room
- You want to choose a heater wattage that suits your tank for the winter
- You want to check whether the flow rate of a canister or top filter suits your tank
- You want to know how many grams of salt make a 0.5% salt bath for goldfish or medaka
- You want to know how many buckets to change in a water change and how many grams of salt to add to the new water
- You want a guideline for how many medaka or goldfish your current tank can hold
Good to know
- Volume is calculated as the "inner dimensions (outer size minus glass thickness)" x the "water level (inner height minus the drop of the water surface)", minus the space taken by substrate grains (the volume excluding gaps) and the share taken by rocks, driftwood and plants.
- Substrate weight is estimated from the weight per liter in the bag (oiso sand 1.6 kg, river sand 1.5 kg, silica sand 1.45 kg, coral sand 1.3 kg, soil 1.0 kg). It can differ by 10 to 20% depending on the product.
- Total weight is the sum of water, substrate and glass, and does not include the stand, filter, lighting or rocks. A caution is shown when the total exceeds the live load standard for residential rooms (1,800 N/m2, about 180 kg/m2, under the Japanese Building Standards Act Enforcement Order), which is a per-square-meter floor standard.
- Heater wattage is based on the rule of thumb of about 1 W per liter of water when the difference between room and water temperature is 10 C, scaled in proportion to the temperature difference. Tanks without a lid lose heat more easily, so a factor of 1.3 is applied.
- The filter flow rate is based on the guideline that the tank water should circulate 5 to 10 times per hour. The figure printed on a product is its maximum flow, so the actual flow will be lower.
- Dechlorinator doses differ by product, so enter the "x mL per x L of water" written on the label of the product you use.
- The salt bath is calculated with table salt (refined salt, 1 teaspoon about 6 g, 1 tablespoon about 18 g). Do not do it in a tank with plants, shrimp, snails, corydoras or other animals sensitive to salt; use a separate container.
- The number you can keep is based on commonly used rules of thumb: 1 L of water per 1 cm of body length for small tropical fish, 1 L per fish for medaka, 10 L per fish for goldfish, and 0.5 L per fish for freshwater shrimp. For treating illness or making husbandry decisions, please also consult a veterinarian or a specialist shop.
- The numbers you enter are saved only in this device's browser and are not sent to a server.
Questions this tool answers
Use Aquarium Water Volume Calculator | Actual Volume, Substrate Amount, Weight, Heater Wattage & Salt Bath for searches like these:
- I want to know the actual water volume of a 60cm tank
- I want to know how many kg of substrate to buy for my tank
- I'm worried the weight of the tank will break the floor
- I want to know what wattage heater to use for my tank
- I want to calculate the amount of salt for a 0.5% salt bath
- I want to know how many mL of dechlorinator to add
- I want to know if my canister filter flow rate is enough
- I want to know how many medaka or goldfish I can keep
FAQ
- How many liters does a 60cm tank actually hold?
- The catalog volume of a standard 60cm tank (60x30x36cm) is about 65 L, but after subtracting the 5mm glass thickness, a water level lowered by 3cm, and 4cm of oiso sand, it actually holds about 52 L. With no substrate and just the water level lowered 3cm, it is about 56 L. A 60cm wide tank (60x45x45cm) holds about 100 L under the same conditions.
- How many kg (how many bags) of substrate does a tank need?
- The volume is the inner floor area times the thickness, multiplied by the weight of each substrate. For a standard 60cm tank with 4cm of oiso sand, that is about 6.8 L, or about 11 kg, which is 3 bags of 5 kg. Soil is sold in liters, so the same tank needs about 6.8 L, or 1 bag of 9 L. Typical thickness is 3 to 5 cm for oiso sand, and for planted-tank soil often 3 cm at the front and 6 to 8 cm at the back.
- What wattage heater should I choose for an aquarium?
- When the difference between room and water temperature is 10 C, about 1 W per liter of water is the guideline. For a standard 60cm tank (actual volume about 52 L) with a room at 15 C and a target of 25 C, you need about 52 W, so choose 80 W. Even in a room that drops to 10 C in midwinter, about 77 W is needed, so 80 W is enough. If you need more than 150 W, splitting it into two heaters gives peace of mind if one fails.
- How many grams of salt make a 0.5% salt bath?
- It is 5 g of salt per 1 L of water. For a 10 L bucket that is 50 g (about 8 teaspoons), and for a 60cm tank with an actual volume of about 52 L it is about 260 g. Adding it all at once stresses the fish, so dissolve it in about 3 portions several hours apart. At water changes, add salt in proportion to the volume of new water to keep the same concentration.
- Can I put a 90cm or 120cm tank on the floor?
- A 90cm standard tank (90x45x45cm) filled with water and substrate weighs about 200 kg including the glass, which is over 500 kg per square meter of its base. The residential floor standard (about 180 kg/m2) assumes a load spread evenly over the whole room, so it does not mean the floor will give way, but a weight exceeding the per-square-meter standard is concentrated on about 0.4 m2. We recommend placing it along the direction of the beams or against a wall, laying a board to spread the weight, and consulting a housing company if you are worried.
- Why does the catalog volume differ from the actual volume?
- Catalog volume is often calculated from outer width x depth x height. In reality the inside is narrower by the glass thickness, the water surface is kept 2 to 3 cm below the rim, and sand is laid on the bottom, so the actual volume is about 20% less than the catalog. Doses of medication, dechlorinator and salt should be calculated from the actual volume, otherwise the concentration may become too strong.
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