Like everyone else, with a tdee calculator like https://tdeecalculator.net
The important thing is to get as much of your calories, macros, and nutrients in as you can. If it takes you more than an hour, take the time if you need it.
When, some 500 days ago, I set out at SW = 97 kg (214 lb), my sedentary TDEE (Mifflin - St Jeor formula; activity factor = 1.2; height = 178 cm (5 ft 10 in)) was estimated around 2.3k kcal/d. Nowadays in maintenance, CW = 63 kg (139 lb) +/- 2 kg (4.4 lb) short-term fluctuations, it’s estimated around 1.9k kcal/d. In hindsight, given that a) I transitioned from SW to CW in roughly 10-12 months (the last couple were a literal crawl), and that b) going by approximate body composition change (initial body fat = 30%; current = 15%) and the assumption that adipose contains 10% water, around 18 kg (40 lb) or 53% of total mass loss was actual fat loss, the rest being combined water and muscle, suggests that my average daily deficit over said period was 18 x 7,700 / 12 x 30 = 385 kcal/d. Since I’ve ended up in maintenance, this more or less aligns with the predicted decline in TDEE of -400 kcal/d.
In practice I didn’t formally calorie-count. I wanted an approach that I could envision myself sustaining indefinitely for the least perceived effort. Eating strictly toward a number didn’t seem like the greatest fit, for one because it didn’t feel practical but more importantly because, knowing that I tend to try a tad too hard (read: obsess) when it comes to optimizing “hard” numeric compliance metrics, I saw the threat of losing the forest for the trees in so doing. Furthermore, my journey was a relatively smooth sail, without month-long plateaus that would compel me to “troubleshoot” my intake.
What I’ve been practicing instead involves a) eating as slowly and mindfully as possible until attaining comfortable satiety, b) sticking for the most part with dietary choices that do not promote over-consumption (not highly processed, not highly palatable, not highly calorie-dense) and c) journaling the day’s food choices (the key difference from formal intake tracking being that journaling reflects on the past, without attempting to explicitly influence the future; of course I still learn from my mistakes as I go, which is the whole point) – what and approximately how much I had (I do a rough conversion to calories just to get an idea), how satiated I felt, and any potential side effects (sleep, digestion, energy levels, to name a few broad classes).
Obviously this strategy can yield days of significant over- or under-eating alike. A restaurant or fast food meal, when gauged just by satiety, can trivially put me on a surplus of several thousand kcal, which is why I limit such instances of prospectively unbounded consumption to 3-5x/month. Home-cooked meals by contrast can easily fall under 1k kcal on absolute while remaining remarkably filling (think dishes based on say Brussels sprouts or chickpeas). Experience has taught me when “supplementation” (e.g. extra bit of dairy or a handful of nuts), an extra serving or even an extra meal is warranted.