The truth is there is no fucking way to estimate caloric expenditure changes from clen+t3 doses. It'll vary enormously per person and also clen's mechanism through which it recomps you is not as simple as just burning calories; it acts directly on the fat cells themselves and even potentially has a lot of anabolic activity in the muscle helping you become leaner through both. there's no human trials on polypharmaceutical enhanced bodybuilders, just use the tried and true clen+t3 protocols for contest prep that basically everyone uses. Could be 2 on 2 off, could be 16-18 weeks straight with ketotefin, could be 8-10 weeks then a two week break then back on, could be jus t8-10 weeks toward the end of prep if you're starting lean. All of it pretty much works, don't worry about being exact with how many calories its burning.
Plus with clen and any other stimulants some of the fat burning is not coming from higher BMR or direct fat cell mobilization, but psyching you up so you accidentally move more throughout the day and from appetite suppression.
I think Palumbo's cookie cutter clen protocol but with like half the t3 he recommends would be a good place to start without fucking yourself up too much and almost certain to get in shape. start around 20-40mcg, raise by 20 every 2 weeks or so until you top out around 120mcg of clen for a few weeks toward the end of 16 weeks. T3 maybe just 25mcg to start and go up to 50mcg as you get closer to contest.... or just keep it right at 25mcg the whole way through since some people get really flat on t3.