About

Women's physiology presents unique advantages and challenges when building muscle. Unlike men, women must navigate hormonal fluctuations that affect metabolic rate, insulin sensitivity, and water retention throughout the month. A static calorie number often fails because your body's energy demands change between the Follicular and Luteal phases.

This calculator is designed with the female hormonal baseline in mind. It accounts for the slight metabolic increase observed during the Luteal phase (pre-period) and adjusts macronutrients to manage cravings and energy levels. It focuses on 'Lean Gains,' recognizing that women typically have a lower threshold for muscle synthesis per month compared to men, making precise caloric surpluses vital to avoid unnecessary body fat.

Formulas

We use the female-specific Mifflin-St Jeor equation as the baseline:

BMR = 10W + 6.25H − 5A − 161

The Cycle Adjustment factor (CA) is added to the TDEE:

Target = (BMR × Activity) + Surplus + CA

Where CA is 0 for Follicular and 200 for Luteal.

Reference Data

Menstrual Phase	Hormonal Profile	Metabolic Impact	Nutritional Adjustment
Follicular (Day 1-14)	Estrogen rising	Normal BMR	Higher Carbs (Better insulin sensitivity)
Ovulation (Day 14)	Estrogen Peak	Slight Peak	Max strength training support
Luteal (Day 15-28)	Progesterone High	BMR +100 to 300 kcal	Higher Fats, slightly more calories

Frequently Asked Questions

Yes. Research indicates that during the Luteal phase (the week or two before menstruation), Basal Metabolic Rate can rise by 2.5% to 11% due to the thermogenic effect of progesterone. This equates to roughly 100-300 extra calories burned per day.

Without performance-enhancing drugs, women can expect to gain about 0.5kg to 0.8kg of muscle per month in their first year of proper training. This rate decreases with training age. This is why a massive caloric surplus usually results in fat gain rather than more muscle.

No. The term 'bulking' refers to the act of eating to grow muscle. Because women have significantly less testosterone than men, it is very difficult to become 'bulky' by accident. You will likely develop a 'toned' and athletic physique.