Articles & guides
212 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.
212 articles
What is TDEE?
TDEE is the total energy you spend in a day: rest, digestion and 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 multiplier table we use, and which number the target is built from.
First principlesNutrition fundamentals4 minHow to calculate your TDEE by hand
Three steps to your TDEE by hand: the Mifflin-St Jeor equation, the exact activity multiplier our calculator uses, and a two-week check against your real 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 one person, and why we use Mifflin-St Jeor.
Human trial dataNutrition fundamentals5 minWhy does every TDEE calculator give a different number?
Different BMR equations, multipliers and rounding add up to gaps of several hundred kcal between calculators. Where each gap comes from and what to do next.
First principlesNutrition fundamentals5 minWhat is NEAT and why does it matter for calories?
NEAT is the energy spent on everything but sleep, food and training. Why it varies so much, how our multiplier adjusts for it, and why it drops on a 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 and job activity combine, and what to do between two levels.
First principlesNutrition fundamentals6 minHow do apps estimate your energy expenditure from your logs?
Adaptive apps back-calculate expenditure from logged intake and trend weight. Why it takes about three weeks, what half-logged days do, and the 3-of-7 rule.
First principlesNutrition fundamentals6 minIs calories in, calories out true?
Calories in, calories out is true as bookkeeping but not as a plan: the out side moves as you diet. What adapts, and why 7,700 kcal per kg is a planning number.
First principlesNutrition fundamentals10 minWhy doesn't exercise burn as many calories as my tracker says?
Wrist trackers miss exercise calories by 20% or more, and the body compensates, so a 400 kcal session adds less. 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 a meal — about a tenth of intake. How it differs by macro and why your TDEE already includes it.
Reference valuesNutrition fundamentals8 minHow many calories should I eat a day?
A calorie target starts from TDEE and moves by a weekly rate of body weight, capped at 35% and held above a floor. The exact rules, 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.