Aquarium Volume Calculator
Our aquarium volume calculator turns your tank’s measurements into an accurate water volume in
gallons or liters. Also called a fish tank volume calculator or aquarium capacity calculator, it
supports rectangular, cube, cylinder, hexagon, bow-front and corner tanks. Knowing your true water
volume is the foundation for every dose, water change and stocking decision you’ll make, so
start here before using any other calculator on this page.
Gallons = (L × W × H in inches) ÷ 231
Open the aquarium volume calculator →
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Aquarium Size Calculator
Not sure how big your tank is? The aquarium size calculator pairs a standard tank dimensions chart
with a custom size tool. Pick a common size (10, 20, 29, 40 breeder, 55, 75, 90, 125 or 180
gallon) or type your own length, width and height to get gallons, liters and filled weight.
It’s the fastest way to confirm aquarium dimensions and tank size before you buy a stand, hood
or light.
Gallons = (L × W × H in inches) ÷ 231
Open the aquarium size calculator & chart →
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Aquarium Substrate Calculator
How much sand do you need? The aquarium substrate calculator estimates the pounds of sand, gravel or
aragonite required for your tank footprint and target bed depth. Different substrates have different
densities, so choosing the right material matters: a deep sand bed weighs far more than a thin
gravel layer. Enter your dimensions and desired depth to get a precise weight before you order, and
avoid the classic mistake of buying one bag too few.
Pounds = (footprint in² × depth in ÷ 1728) × density (lb/ft³)
Open the aquarium substrate calculator →
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Aquarium Stocking Calculator
The aquarium stocking calculator gives you a conservative, honest estimate of how many fish your tank
can support. Instead of the outdated one-inch-per-gallon rule, it weighs your water volume against
adult fish size and bioload. Use it as a sanity check, not gospel. Filtration, feeding and
species temperament all matter. When in doubt, understock: a lightly stocked tank is more stable,
easier to keep and healthier for everything living in it.
Open the aquarium stocking calculator →
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Saltwater Mix Calculator
The saltwater mix calculator tells you exactly how much salt mix to add to reach your target
salinity. Whether you’re mixing a fresh batch for a water change or filling a new build, enter
your water volume and desired specific gravity to get the amount of salt you need. It’s the
aquarium salt calculator and salinity calculator we reach for whenever we mix water on the farm, so
you hit 1.026 the first time instead of chasing your numbers.
Open the saltwater mix calculator →
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Alkalinity Dosing Calculator
Alkalinity is the single most important parameter to keep stable in a reef tank. This alkalinity
dosing calculator works out how much buffer to add to move your current dKH to your target, and
splits large corrections over several days so you don’t shock your corals. Enter your volume,
current and desired alkalinity, and choose your product to get a precise milliliter dose for the
whole tank.
Dose (mL) = (target dKH − current dKH) × liters ÷ product factor
Open the alkalinity dosing calculator →
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Calcium Dosing Calculator
Calcium fuels coral skeletal growth alongside alkalinity and magnesium. The calcium dosing calculator
estimates how much supplement to add to raise your calcium to a target ppm for your exact water
volume. Dose calcium and alkalinity in balance; chasing one while ignoring the other is the
fastest way to crash your numbers. Always retest before making another large adjustment.
Open the calcium dosing calculator →
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Magnesium Dosing Calculator
Magnesium keeps calcium and alkalinity in solution, which is why stubborn alk and calcium problems
are so often a magnesium problem in disguise. This magnesium dosing calculator estimates the
supplement needed to reach your target ppm for your tank’s volume. Correct magnesium first,
then dial in alkalinity and calcium, and your whole reef chemistry becomes far easier to hold steady.
Open the magnesium dosing calculator →
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GFO Media Calculator
GFO (granular ferric oxide) is the workhorse of phosphate control. Our GFO calculator (the
tool reefers already find when they search “gfo calculator”) recommends a sensible
starting amount of media for your water volume and phosphate level, and it covers popular brands like
RowaPhos and Phosphate Rx. Start low, run it in a reactor or media bag, and increase gradually to
avoid dropping phosphate too fast.
Open the GFO media calculator →
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Activated Carbon Calculator
Activated carbon polishes water, removes discoloration and pulls out dissolved organics and toxins.
The activated carbon calculator estimates how much carbon your aquarium needs based on water volume,
so you’re not guessing with a random handful. Change it on a regular schedule and run it in a
reactor or high-flow bag for the clearest, best-smelling water your tank has ever had.
Open the activated carbon calculator →
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Aquarium Weight Calculator
Before you set up a new tank, find out what it actually weighs when full. The aquarium weight
calculator adds water at 8.34 pounds per gallon to the glass or acrylic and your substrate to
estimate total filled weight. It’s essential for checking whether your floor, stand and
location can safely handle the load. A modest 75-gallon reef can easily top 800 pounds once
it’s running.
Water weight (lb) = gallons × 8.34
Open the aquarium weight calculator →
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Aquarium Heater Size Calculator
Sizing your heater correctly keeps your tank stable and your fish safe. The aquarium heater size
calculator recommends wattage from your water volume and the difference between room temperature and
your target temperature. As a rule of thumb you’ll want roughly 3 to 5 watts per gallon,
more in a cold room. Two smaller heaters are often safer than one large one. If one sticks on
or fails, the damage is limited.
Watts ≈ gallons × 3 to 5 (higher for a bigger temperature gap)
Open the aquarium heater size calculator →
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Kalkwasser Calculator
Kalkwasser (limewater) is a classic, inexpensive way to maintain calcium and alkalinity while
stabilizing pH. This kalkwasser calculator helps you mix and dose it correctly for your evaporation
top-off. Dose slowly through your ATO and never overshoot. Kalk is potent, and steady beats
strong every time in a reef tank.
Open the kalkwasser calculator →
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Biopellet Calculator
Biopellets drive natural nutrient export by feeding bacteria that consume nitrate and phosphate. The
biopellet calculator gives you a conservative starting volume for your reactor based on tank size.
Start under the recommendation, ramp up slowly, and watch your parameters: too many pellets
too fast can strip nutrients and stress corals.
Open the biopellet calculator →
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Phytoplankton Dosing Calculator
Phytoplankton feeds copepods, filter feeders and many corals, building a richer, more natural reef.
This phytoplankton dosing calculator suggests a dose based on your water volume, following the same
approach we use across our coral farm. Start small, dose consistently, and let your clean-up crew and
corals tell you when to adjust.
Open the phytoplankton dosing calculator →
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Live Rock Calculator
Live rock is the biological and structural backbone of a reef aquarium. The live rock calculator
estimates how many pounds you need for your tank size and desired aquascape density. Modern
aquascapes use less rock than the old one-to-two-pounds-per-gallon rule. Open structure means
better flow, easier maintenance and more room for corals to grow.
Open the live rock calculator →
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Aquarium Electricity Cost Calculator
Reef tanks run 24/7, and the power adds up. The aquarium electricity cost calculator estimates your
monthly running cost from your equipment’s wattage, hours of use and your local power rate. Use
it to compare pumps, heaters and lights, and to see where an efficient upgrade will actually pay for
itself.
Open the aquarium electricity cost calculator →
