Feline Grimace Scale (FGS) Calculator
The Feline Grimace Scale (FGS) is a validated, observer-based pain score for acute pain in cats. Score five facial action units (each 0-2) for an objective total out of 10. Total ≥ 4 indicates analgesia is needed.
Ear position
Position of the pinnae relative to the head.
Orbital tightening
Tightening / narrowing of the eyelids.
Muzzle tension
Tension and shape of the muzzle (top-down view).
Whisker position
Curvature and position of the whiskers.
Head position
Position of the head relative to the line of the shoulders.
How to use this tool
What the FGS measures
Five facial action units that reliably change with acute pain in cats: ear position, orbital tightening (squinting), muzzle tension, whisker position, and head position. Developed and validated by the Animal Welfare and Pain Research Group at Université de Montréal (Evangelista et al., 2019).
Score from a distance
Observe the cat undisturbed - in their cage, from a distance, or on a brief video. Handling and approach alter facial expressions and skew the score. The FGS website (felinegrimacescale.com) has comparison photos for each AU score that are worth bookmarking.
Analgesia threshold
Total ≥ 4/10 indicates pain requiring intervention. After analgesia (e.g. buprenorphine 20 μg/kg OTM, methadone 0.2 mg/kg IM, robenacoxib 1-2 mg/kg SC), reassess at 30 minutes - score should decrease by at least 1-2 points if analgesia was effective.
Where it's useful
Post-operative (ovariohysterectomy, dental, orthopaedic), hospitalised medical patients, trauma cases, chronic pain reassessment. Validated in cats > 4 months. Less reliable in extremely young kittens and unconscious patients.
Frequently asked questions
What is the Feline Grimace Scale?
A validated observer-based acute pain score for cats. Five facial action units - ear position, orbital tightening (squinting), muzzle tension, whisker position, head position - each scored 0-2. Total 0-10.
What FGS score indicates a cat needs analgesia?
Total ≥ 4/10 triggers analgesia. Reassess 30 minutes after the intervention - score should drop by 1-2 points if effective.
How should I observe the cat for FGS scoring?
From a distance, undisturbed - handling alters facial expressions and skews the score. A brief video can be useful. The FGS validation studies emphasised "observer who is not interacting with the cat".