💞 Second-Cat Compatibility Checker
Most failed two-cat homes didn't fail on love — they failed on matching. A bouncing kitten and a dignified senior, a cat-social butterfly and a solo artist: the friction is predictable before anyone comes home. Describe your resident cat, then test a specific candidate — or let the checker recommend the profile most likely to fit your household.
Your resident cat
The candidate
Compatibility
Friction points & how to handle them
Whatever the score, the introduction decides the outcome: use the New Cat Introduction Planner for a stage-by-stage plan, and the Multi-Cat Resource Calculator to check your litter boxes, bowls and space add up for two.
Why check before you adopt?
🎯 Mismatches are predictable
Shelters see the same returns again and again: kitten energy vs senior dignity, a solo-preferring resident, two unneutered adults. Every one of those is visible on paper before the carrier opens. This checker makes the invisible obvious.
💞 It's for the resident, too
A second cat is often adopted "as a friend" for a cat who never asked for one. If your resident prefers solo life, the kindest match may be no match — and the checker will say so honestly rather than sell you a fairy tale.
🗓️ Score is the start, not the verdict
Even a 95% pairing can fail a rushed introduction, and a 45% pairing can thrive with a slow one. The score tells you where the friction will be; the introduction plan tells you what to do about it.
Questions, answered
Is a kitten always the easiest second cat?
Kittens are socially flexible and rarely read as rivals, so many adult cats accept them — but a kitten's energy can overwhelm an older or shy resident, and the kitten still grows into an adult whose personality you're guessing at. Young-adult pairings (1–3 years) are often the sweet spot: known personality, matched energy, decades of overlap.
Which sex pairing works best?
Among neutered cats, differences are mild tendencies, not laws: mixed pairs and female pairs are often smooth, two adult males can be perfectly fine or mildly competitive depending on the individuals. Unneutered adults of any pairing are the genuinely hard mode — hormones turn introductions into negotiations between governments. Neutering first is the single easiest compatibility upgrade.
My resident cat has never met another cat. Is that a red flag?
Not necessarily — it means "untested", not "hostile". Many solo-raised cats adapt well with a genuinely slow introduction. The checker scores unknown history slightly below proven history, and the intro planner's early stages (scent before sight) exist precisely for this cat.
Compatibility scores summarise population-level tendencies from shelter and behaviourist experience — individual cats break every rule, in both directions. A low score is a prompt to plan carefully or reconsider, never a judgement on either cat.