Calculating RCR for indoor cats

I've been trying to figure out the exact Resting Caloric Requirement (RCR) for my cats because I want to be precise with their food portions. I know the general formula is around 100 times their weight in pounds, but I'm not sure how to adjust for activity level or age.

For instance, Holly is 8 years old and on thyroid meds, while Ivy is 4 and healthy. Do I use the same baseline for both, or does the thyroid medication change the calculation significantly? I want to make sure I'm not underfeeding the older one but also not overfeeding the younger one.

Honestly, I just eyeball it based on their body condition score. Biscuit and Whiskers are both 6 years old and similar weight, so I feed them the same amount. If they look too thin, I add a bit more. If they start looking round, I cut back.

I found this method way easier than doing math every day. Dealing with a cat who begs for food has some tips on ignoring the begging, which helps me stick to the portions I've decided on.

I appreciate the simplicity, but for a precise approach, I stick to the RCR formula: 100 x weight (lbs) x 0.7 for indoor cats. I then adjust by 10-15% if the cat is very active or underweight.

For my cats, Nacho (5 DSH) and Gordo (7 mix), I calculate their individual needs. Gordo is calmer, so I keep his portion on the lower end of the adjustment range. This ensures consistency. If a cat refuses to eat, I check When to worry about refusal to eat to rule out medical issues before assuming they are just being picky.

The formula is fine, but the execution is tricky if you have multiple cats. Miso is 2 and hyper, while Gus is 5 and more sedentary. Their caloric needs are different, but they often try to share bowls.

I separate them during feeding time. Feeding cats separately explains how I set up my feeding stations. It’s a hassle, but it ensures Miso doesn’t steal Gus’s food, which would mess up the calorie tracking completely.

I’m new to this. Koda is 1 and just adopted, Kiki is 5 and anxious. I’m worried I’m feeding Koda too much because he’s so small. The formula gives me a very low number. Is that right for a kitten/young adult? I’m also concerned about Kiki’s stress affecting her appetite. Should I use the same formula for her if she’s eating less due to anxiety?