What this calculator does
Litter use is set by tray geometry and habit, not by the number of cats, which is why two households with the same cats can be a hundred dollars a year apart. Three trays at 45 by 35 cm filled 5 cm deep hold 7.88 litres each. Changed out completely once a month with half a litre a week of top-up, that is 30 litres a month, two 15-litre bags, and about $36.
The part people get wrong is comparing a clumping routine with a non-clumping one as though they were the same purchase. Clumping litter is scooped daily, topped up, and fully changed rarely. Non-clumping is tipped out and refilled often, sometimes weekly. At one full change a month this costs $36.17; at two it is $64.52 and at four it is $121.22. The litre price on the bag tells you almost nothing without that frequency beside it.
The formula
A tray holds length × width × depth in cubic centimetres, and dividing by a thousand gives litres. Monthly use is trays × (complete changes × litres per fill + weekly top-up × 4.345), where 4.345 is the average number of weeks in a month. Bags and cost follow from the bag size and price you enter, so any litter, any bag and any currency work.
| Term | Meaning |
|---|---|
| Complete change | Tipping the tray out and refilling it. The main driver of consumption. |
| Top-up | Litter added after scooping to keep the depth up. Small each time, constant over a month. |
| Litres per fill | What one tray holds at your chosen depth. |
| Trays recommended | The usual guidance is one tray per cat plus one spare. |
The inputs explained
| Field | What to enter |
|---|---|
| Cats | Cats in the household. Used for the per-cat cost and the tray recommendation. |
| Litter trays | Trays you actually keep filled, which may be more or fewer than the recommendation. |
| Tray length (cm) | Internal length of the tray, not the outside of the moulding. |
| Tray width (cm) | Internal width of the tray. |
| Litter depth (cm) | Depth of litter. Most guidance is 5 to 7 cm; clumping needs the depth, non-clumping less so. |
| Complete changes (per month) | Complete changes per month. Weekly is roughly 4.3, fortnightly 2.2, monthly 1. |
| Top-up after scooping (L per tray per week) | Litter added per tray per week after scooping. Half a litre is typical with clumping litter. |
| Bag size (L) | Bag size in litres. If yours is sold by weight, the litre volume is usually on the back. |
| Bag price ($) | What you pay for that bag. |
When to use it
Working out a monthly budget
Enter your trays, depth and real change frequency. The per-cat figure is the one to use when a household splits costs.
Comparing two litters
Run it twice with each bag price and each realistic change frequency. A cheaper bag changed twice as often is not cheaper.
Deciding how deep to fill
Depth scales cost directly, so going from 5 cm to 8 cm is a 47 per cent increase in litter. Deep enough to dig matters; deeper than that is spending.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much does changing the litter more often cost?
Only the number of complete changes a month changes.
| Complete changes | Litter cost a month | Litter used a month | Days a bag lasts |
|---|---|---|---|
| 0.5 a month | $22.00 | 18.3 L | 25 days |
| 1 a month | $36.17 | 30.1 L | 15 days |
| 2 a month | $64.52 | 53.8 L | 8 days |
| 4 a month | $121.22 | 101.0 L | 5 days |
| 8 a month | $234.62 | 195.5 L | 2 days |
What does litter depth cost?
Only the depth of litter in the tray changes.
| Litter depth | Litter cost a month | Litter per complete fill | Litter used a month |
|---|---|---|---|
| 3 cm | $24.83 | 4.73 L per tray | 20.7 L |
| 4 cm | $30.50 | 6.30 L per tray | 25.4 L |
| 5 cm | $36.17 | 7.88 L per tray | 30.1 L |
| 6 cm | $41.84 | 9.45 L per tray | 34.9 L |
| 8 cm | $53.18 | 12.60 L per tray | 44.3 L |
Questions
How many trays should I have?
The common veterinary guidance is one per cat plus one, so three for two cats, placed apart rather than in a row. The calculator shows that figure but costs whatever number you actually keep.
My litter is sold by weight, not litres.
The litre volume is usually printed on the bag as well. If not, weigh out a measured litre once and divide, since litter densities vary by more than you would expect between clay, crystal and plant-based types.
Does the number of cats not drive the cost?
Less than people expect. Cats drive how often the tray needs attention, but the litter consumed is set by how many trays you fill, how deep, and how often you empty them. That is why the calculator asks for those rather than guessing from head count.
Is a deeper tray cheaper in the long run?
No, deeper means more litter per fill and so more cost, unless the depth lets you go longer between complete changes. If it does, run the calculator twice and compare, because that trade is real and depends on your litter.
What about the cost of the rest of it?
Not included. Trays, liners, mats, deodoriser and disposal bags are their own line, and the pet cost calculator is the place for a full picture.
For the whole household budget there is cost of owning a pet, and dog and cat daily calories covers feeding. Cat age in human years is the other page people come here for.