Articles & guides
125 pieces on the questions people actually search — how many calories, how much protein, how big a deficit, what a set at RIR 2 means, how the 1RM estimate works, how many sets a week — with every number derived from the formulas the apps use or cited to a source you can open. Training and nutrition education only; never medical advice.
125 articles
What is TDEE?
TDEE is the total energy you spend in a day: resting metabolism plus digestion plus movement. What it is made of, how a calculator estimates it, and how far off it can be.
Reference valuesNutrition fundamentals4 minBMR vs TDEE: what's the difference?
BMR is what your body spends at complete rest; TDEE adds digestion and movement on top. The exact multiplier table our calculator uses, and which number the target is built from.
First principlesNutrition fundamentals4 minHow to calculate your TDEE by hand
Three steps to your TDEE with a pen: the Mifflin-St Jeor equation, the exact activity multiplier our calculator uses, and a two-week check against real intake and weight data.
First principlesNutrition fundamentals5 minMifflin-St Jeor vs Harris-Benedict vs Katch-McArdle: which BMR formula is best?
The four common BMR equations side by side — what each needs as input, how far off they typically are for an individual, and why our calculator uses Mifflin-St Jeor.
Human trial dataNutrition fundamentals5 minWhy does every TDEE calculator give a different number?
Different BMR equations, different activity multipliers and different rounding add up to gaps of several hundred kcal between calculators. Where each gap comes from and what to do with the number.
First principlesNutrition fundamentals5 minWhat is NEAT and why does it matter for calories?
NEAT is the energy you spend on everything that is not sleeping, eating or training. Why it is the most variable part of your day, how our multiplier adjusts for it, and why it drops when you diet.
Reference valuesNutrition fundamentals5 minWhich activity level should I pick on a calorie calculator?
The five activity levels on our calorie calculator, the exact multiplier behind each, how training days and job activity combine, and what to do if you sit between two levels.
First principlesNutrition fundamentals6 minHow do apps estimate your energy expenditure from your logs?
Adaptive apps back-calculate expenditure from what you logged and how trend weight moved. Why it takes about three weeks, what a half-logged day does to it, and the 3-of-7 rule MacroDiet uses.
First principlesNutrition fundamentals6 minIs calories in, calories out true?
Calories in, calories out is true as bookkeeping and misleading as a plan: the "out" side moves when you diet. What adapts, why 7,700 kcal per kg is a planning number, and what it means for tracking.
First principlesNutrition fundamentals6 minWhy doesn't exercise burn as many calories as my tracker says?
Two reasons: wrist trackers overstate exercise energy by 20% or more, and the body compensates so a 400 kcal session adds less than 400 kcal to the day. Why we never add exercise calories back.
Human trial dataNutrition fundamentals5 minWhat is the thermic effect of food?
The thermic effect of food is the energy spent digesting and storing a meal — roughly a tenth of what you eat. How it differs by macronutrient and why it is already inside your TDEE estimate.
Reference valuesNutrition fundamentals8 minHow many calories should I eat a day?
A calorie target starts from TDEE and moves by a rate of body weight per week, capped at 35% and held above a floor. The exact rules our calculator applies, with three worked examples.
First principlesZyra is a training and nutrition tracking tool. Nothing on this page is medical advice, a diagnosis, or an individual prescription. The numbers are estimates from published formulas and the apps' own rules — consult a qualified professional for decisions about your health, and a coach for your training.