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The number is the easy part
Every nutrition calculator online hands you a figure and walks away. These hand you the figure and then show you the day it has to fit inside. Hour by hour, meal by meal.
The tools
Five calculators, free and without an account. Pick the question you actually have.
Why these look different
A daily target is not a daily instruction. Knowing you need 2.4 liters of water does not tell you that you should already be at 900 ml by lunch, and that is the part that decides whether you hit it. So every tool here ends in a strip of a real day with your target laid across it. That is the same arithmetic the Mango Bites app runs on your phone. The web version just shows its work.
Where the numbers come from
Each tool states its formula in full and links the guideline it came from. Nothing here is proprietary magic: Mifflin-St Jeor for energy, the US Dietary Guidelines for fiber, the ISSN position stand for protein. Where Mango Bites uses a house rule instead of the generic one (the hydration goal is the clearest case) the page says so and explains why.
This is an estimate, not medical advice. Formulas like these describe averages, and you are a person rather than an average. Medication, thyroid conditions, pregnancy, breastfeeding and a history of disordered eating all move these numbers. Talk to a doctor or a registered dietitian before making a big change.