Your calorie target is only as good as the equation behind the calculator. The National Academies of Sciences, Engineering, and Medicine updated its energy equations in the 2023 Dietary Reference Intakes, replacing the previous Estimated Energy Requirement formulas with new equations that are designed to better account for body size, age and physical activity. Many free TDEE calculators, however, still estimate daily needs with the older Mifflin-St Jeor equation or an earlier EER formula. That gap means your maintenance or deficit number may be out of step with current guidance, and a weekly plan can help you use whatever number you arrive at more realistically.
Why the underlying equation shifts your TDEE
TDEE calculators follow a simple chain: they estimate basal metabolic rate, then multiply that number by an activity factor. If the basal equation is outdated, every downstream number—maintenance calories, deficit targets, macro splits—moves with it. The Mifflin-St Jeor equation is still widely used because it is short and easy to implement, but it is not the updated 2023 NASEM approach. A calculator that names Mifflin-St Jeor as its method is, by definition, not using the newer formulas. When a tool does not disclose its equation, treat that as a reason to check with the provider before relying on the output.
What the 2023 NASEM update changes
The exact coefficients of the new equations are not reproduced here, so specific validation results cannot be quoted from this article. What you can verify directly is whether a calculator cites the 2023 NASEM Dietary Reference Intakes or still references older EER equations. If you need the formulas themselves, the National Academies publication is the authoritative place to look, and peer-reviewed validation studies can show how the equations perform in populations similar to yours. Without those numbers, avoid adjusting your intake by large jumps; first confirm which equation your current tool uses.
How to audit your calculator quickly
Start with the method page. Does it say Mifflin-St Jeor, Harris-Benedict, Katch-McArdle, or an older EER? If it does not mention NASEM 2023 or the 2023 DRI, it may be running pre-2023 formulas. Second, check whether the tool asks for body composition; some formulas use body fat, others race or sex in ways the updated EER may handle differently. Third, compare results from at least two calculators that document their equations. If the updated equation is available in one of them, that comparison tells you how much your old target may have shifted.
Plan a weekly deficit instead of a daily pass/fail
Once you settle on an updated TDEE, a weekly calorie budget can reduce the pressure of a single daily number. Instead of eating the same amount every day, set a seven-day total and allow yourself lower days and higher days around training, work or social meals. A Danish-language week-number calendar at Uge Kalender gives week numbers, week dates, holidays and a printable annual calendar, so you can mark planned higher and lower days at a glance. The page is in Danish, but the week grid and numbers are easy to read even if you do not speak the language.
Your next step
Find out which equation your calculator uses before you change your intake. If it is not the 2023 NASEM update, look for a tool that documents the newer formulas, then transfer your target into a weekly plan. The goal is not to obsess over a single daily number but to make your estimate current and your execution flexible.