Fitness calculators
Nine calculators, two apps' worth of math, every formula shown next to its result. The nutrition tools run the same v2 algorithm MacroDiet uses to set targets; the training tools run the same functions Zyra Workouts uses for one-rep max, plate loading, RIR and weekly volume. Runs in your browser — nothing you type is sent anywhere.
Nutrition
Mifflin-St Jeor, an activity multiplier, rate-based deficits and surpluses with caps and floors, and a protein tier table.
Macro calculator
Daily calories and protein, fat and carb grams from the MacroDiet v2 formula.
Open calculator →Calorie calculator
BMR (Mifflin-St Jeor), activity multiplier and TDEE, with maintain / lose / gain targets.
Open calculator →Calorie deficit calculator
Weekly rate to a daily deficit, with the 35% cap and calorie floors the algorithm applies.
Open calculator →Protein calculator
Grams per day from body weight and a protein tier — the same table MacroDiet uses.
Open calculator →Training
Brzycki and Epley estimates, plate decomposition from your inventory, the RIR ↔ RPE ladder, warm-up ramps and per-muscle weekly sets.
1RM calculator
Estimated one-rep max from a set (Brzycki to 12 reps, Epley above) and a rep-max table.
Open calculator →Plate calculator
Plates per side for a target bar weight from your plate inventory, in kg or lb.
Open calculator →RIR / RPE converter
Reps in reserve to rate of perceived exertion and back, with the app's clamps.
Open calculator →Warm-up set builder
A warm-up ramp to a top set, every row rounded to a load you can actually put on the bar.
Open calculator →Weekly sets calculator
Working sets per muscle for a planned week against the app's landmarks, plus a balance score.
Open calculator →Per-exercise 1RM calculators
The one-rep max estimate with each exercise's own defaults and a load chart alongside — 49 loadable exercises from the exercise library:
The formulas
- Energy. BMR = 10·kg + 6.25·cm − 5·age + (5 | −161), then TDEE = round(BMR × multiplier) with the multiplier from training days per week and daily movement. Deficits and surpluses are a weekly rate in % of body weight × 7,700 kcal/kg ÷ 7, capped at 35% of TDEE, with calorie floors on a cut.
- Macros. Protein kg × {1.2, 1.6, 2.0, 2.4} (+0.2 when losing), fat as a share of what is left by diet style with a floor of max(0.6 g/kg, 20% kcal), carbohydrate fills the remainder at 4 kcal/g.
- Strength. 1RM = w × 36 ÷ (37 − r) up to 12 reps (Brzycki), w × (1 + r/30) above (Epley); plates per side (total − bar) ÷ 2 greedy over the inventory; RIR = 10 − RPE clamped to the app's 6–10 scale.
Every constant, its source file, and the worked examples are on the methodology page.
Zyra 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.