A proper macro calculator: it uses your body fat percentage when you have it (far more accurate than weight alone), lets you control exactly how aggressive your deficit or surplus is, and can split your carbs between training and rest days — the same approach used in real coaching plans.
Knowing your body fat % lets us calculate from lean body mass (Katch-McArdle) instead of total weight (Mifflin-St Jeor) — this is meaningfully more accurate for anyone leaner or heavier than average.