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Aquarium Substrate Calculator

Work out how much gravel, sand or aqua soil your tank needs from its shape, footprint and the substrate depth you want.

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Aquarium Substrate Calculator is free to use as often as you like, directly from this page. You will find it under Pets & animals, with Aquarium Heater Wattage Calculator and Bird Cage Size Calculator for the neighbouring cases.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What is Aquarium Substrate Calculator?

Work out how much gravel, sand or aqua soil your tank needs from its shape, footprint and the substrate depth you want.

When would I actually use this?

Day-to-day care: how much to feed at a given weight, whether a size is right for the breed, and what a life stage means in human terms.

What is the most common mistake?

Using the seven-years rule for a dog's age. Ageing is fast in the first two years and then slows, and it slows much more for a small breed than for a large one — the multiplier is not a constant.

How is Aquarium Substrate Calculator different from Aquarium Heater Wattage Calculator?

They sit next to each other but answer different questions: Aquarium Heater Wattage Calculator is the one to open when you need it to find the heater wattage your tank needs from its volume, the target water temperature and the coldest room temperature. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

Bird Cage Size Calculator is the closest one after this: Minimum cage dimensions and safe bar spacing for eleven species, from finches to macaws, in inches and centimetres.

What else is worth having open alongside it?

Cat Calorie Calculator and Cat Litter Box Calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Portions follow published feeding guidelines by species and weight; age equivalences use the size-dependent curves rather than a flat multiplier. None of this replaces a veterinarian, especially for an animal that is unwell.

Further reading

All guides →
How-toHow Much Substrate Does an Aquarium Need? Depth, Weight and Grain SizeThe depth follows the job: a bare display, a planted tank whose roots need room, an under-gravel plate. Then comes the number people are unprepared for — substrate is what puts a filled tank past what a piece of furniture can hold. Plus why fine sand compacts and coarse gravel traps waste.How-toWhat Wattage of Heater Does an Aquarium Need? Volume Is Only Half the AnswerThe same tank needs a 100 W heater in a warm flat and 300 W in an unheated room. The variable is the gap between the water and the room, which most rules of thumb drop entirely. Plus why two smaller heaters beat one big one, and where this calculator's recommendation stops being trustworthy.ExplainerHow Many Fish Can a Tank Hold? The Inch-per-Gallon Rule Is WrongEvery stocking calculator implements a length-per-volume rule, and waste output scales with body mass, not length. A fish twice as long makes nearly five times the ammonia. Run through the tool's five methods, the same tank comes back holding anywhere from 6 to 12 fish.How-ton + 1 Litter Boxes, and What the Litter Actually CostsTwo cats need three boxes, not two, and each should be one and a half body lengths long — 69 cm for an average adult. The litter figure that follows is larger than most people expect, and knowing why is the useful part.How-toThe IATA Crate Formula an Airline Measures at Check-InLength A + half B, width twice C, height D. The width rule is the one that fails people: a dog with 28 cm shoulders needs 56 cm of interior width, and no crate sold by weight rating tells you that.ExplainerHow Many Calories Should a Cat Eat? The Arithmetic, and Where It StopsResting energy scales with weight to the power 0.75, not linearly, which is why a chart that doubles the food for a cat twice the weight is 83 kcal a day over. Neutered against intact, indoor against outdoor, and the boundary the arithmetic must not cross.