What health calculators does Texterfly offer?

Texterfly offers 3 free health calculators: a BMI Calculator (adult and child/teen modes, visual gauge, healthy weight range), a Calorie & Macro Calculator (Mifflin-St Jeor and Katch-McArdle formulas, macronutrient breakdown, goal-based timeline), and a Pregnancy Due Date Calculator (last menstrual period or conception date methods, trimester guide, weekly development milestones). All are for informational purposes only.

What do the BMI categories mean?

BMI (Body Mass Index) categories for adults are: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), Obese Class I (30–34.9), Obese Class II (35–39.9), and Obese Class III (40 and above). Note that BMI has significant limitations — it does not account for muscle mass, bone density, age, sex, or ethnicity. Athletes may have a high BMI due to muscle, not fat. Always consult a healthcare professional for a full health assessment.

What is the Mifflin-St Jeor formula?

The Mifflin-St Jeor formula estimates Basal Metabolic Rate (BMR) — calories burned at rest. For men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5. For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161. Multiplying BMR by an activity factor gives TDEE (Total Daily Energy Expenditure), which is the estimated number of calories needed to maintain current weight.

TDEE (Total Daily Energy Expenditure) is the estimated total number of calories you burn per day, including physical activity. It is calculated by multiplying your BMR (Basal Metabolic Rate) by an activity factor: Sedentary (×1.2), Lightly active (×1.375), Moderately active (×1.55), Very active (×1.725), Extra active (×1.9). To lose weight, eat fewer calories than your TDEE; to gain, eat more.

How is a pregnancy due date calculated?

The most common method is Naegele's rule: add 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP). For example, if your LMP was January 1, the estimated due date is October 8. Alternatively, add 266 days to a known conception date. Only about 5% of babies are born on their exact due date — it's an estimate within a 2-week window.

What are the pregnancy trimesters?

First Trimester: Weeks 1–12 (months 1–3). Key developments: fertilisation, heart formation, organ development. Second Trimester: Weeks 13–26 (months 4–6). Key developments: movement felt, sex identifiable, rapid growth. Third Trimester: Weeks 27–40+ (months 7–9+). Key developments: lungs mature, weight gain, preparation for birth.

Are these calculators a substitute for medical advice?

No. These calculators are for informational and educational purposes only. They are not designed to diagnose, treat, cure, or prevent any medical condition. BMI, calorie needs, and pregnancy timelines are estimates based on statistical formulas — individual health varies significantly. Always consult a qualified healthcare professional, doctor, or registered dietitian for personalised medical guidance.

How accurate is the BMI calculator?

The BMI formula is mathematically accurate — it correctly calculates weight (kg) divided by height (m²). However, BMI as a health metric has well-documented limitations: it does not distinguish between fat and muscle, does not account for where fat is stored (visceral vs subcutaneous), and may misclassify athletes as overweight and elderly people with muscle loss as normal weight. Use BMI as one data point, not a definitive measure of health.

Are these health calculators free?

Yes. All 3 health calculators are 100% free with no registration, subscription, or payment required.

Is my health data private?

Yes. All calculations run entirely in your browser. Your weight, height, age, activity level, and other personal health data are never sent to any server or stored anywhere.

How many calories should I eat to lose weight?

A safe calorie deficit for weight loss is 250–500 calories below your TDEE, which produces 0.25–0.5 kg (0.5–1 lb) of fat loss per week. Use this calculator to find your TDEE, then subtract 500 for the standard weight loss target.

TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns in a day, including basal metabolism, physical activity, and the energy used to digest food. Eating at your TDEE maintains your current weight.

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to maintain basic functions like breathing, circulation, and organ function. It represents 60–75% of most people's total calorie burn.

What is the Mifflin-St Jeor formula?

The Mifflin-St Jeor formula calculates BMR using height, weight, age, and sex. For men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5. For women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161. It is the most accurate formula for the general population.

How many grams of protein should I eat per day?

General guidelines: 0.8g per kg of body weight for sedentary adults. 1.6–2.2g per kg for those trying to build muscle or maintain muscle during weight loss. Use the macro calculator above with the High Protein plan to calculate your personal target.

What is a safe rate for weight loss?

A safe and sustainable rate is 0.25–0.5 kg (0.5–1 lb) per week, requiring a daily deficit of 250–500 calories. Losing faster than 1 kg per week risks muscle loss, nutrient deficiencies, and metabolic slowdown.

What are macronutrients?

Macronutrients are protein (4 kcal/g), carbohydrates (4 kcal/g), and fat (9 kcal/g). Every calorie in your diet comes from these three sources. Tracking macros rather than just calories gives you more control over body composition, energy levels, and satiety.

Why is my weight loss stalling?

As you lose weight, your BMR decreases because a lighter body burns fewer calories. This is metabolic adaptation. Recalculate your TDEE with your new weight and adjust calories. Also verify food tracking accuracy — portion estimation errors are very common.

Back to Health & Fitness

Calorie & Macronutrient Calculator

Calculate your daily calorie needs and macros using Mifflin-St Jeor or Katch-McArdle. Get TDEE, weight loss/gain targets, and protein/carb/fat breakdown across 4 diet plans.

Mifflin-St JeorKatch-McArdleTDEE Calculator4 Diet PlansMacro BreakdownMetric & Imperial100% Free

Calorie & Macro Calculator

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How This Calorie Calculator Works

This calculator uses two of the most scientifically validated BMR formulas, multiplied by an activity factor to give your TDEE — then adjusts for your specific weight goal and breaks the result into macronutrients.

# Mifflin-St Jeor formula

Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5

Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161

# Katch-McArdle formula (athletes)

BMR = 370 + (21.6 × Lean Body Mass in kg)

# TDEE

TDEE = BMR × Activity Multiplier

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Two BMR Formulas

Mifflin-St Jeor is the gold standard for the general population. Katch-McArdle is more accurate for athletes because it accounts for lean body mass.

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Activity Multipliers

5 activity levels from sedentary (×1.2) to extra active (×1.9) account for how your daily movement affects your total calorie burn.

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4 Diet Plans

Balanced, Low Carb, High Protein, and Keto — each splits your calorie target into grams of protein, carbs, and fat with a visual donut chart.

Macronutrient Reference — All 4 Diet Plans

Diet Plan	Protein	Carbs	Fat	Best For
Balanced	30%	40%	30%	Good for general health and body recomposition
Low Carb	40%	25%	35%	Effective for fat loss and blood sugar control
High Protein	40%	30%	30%	Optimal for muscle building and satiety
Keto	25%	5%	70%	Very low carb, high fat for ketosis

Activity Level Multipliers (Harris-Benedict Scale)

Activity Level	Multiplier	Exercise Description	Example
Sedentary	× 1.2	Little or no exercise	Desk job, minimal walking
Lightly Active	× 1.375	Light exercise 1–3 days/week	Walking, yoga, light gym
Moderately Active	× 1.55	Moderate exercise 3–5 days/wk	Jogging, cycling, gym 4×/wk
Very Active	× 1.725	Hard exercise 6–7 days/week	Daily intense training
Extra Active	× 1.9	Very hard exercise or physical job	Athlete or manual labourer

Frequently Asked Questions

How accurate is this calorie calculator?: The Mifflin-St Jeor formula has been validated in multiple studies and is considered the most accurate for the general population, with average error rates of 10–15%. The Katch-McArdle formula is more accurate for athletes and lean individuals. Individual metabolism can vary by up to 20%, so treat results as a starting point and adjust based on real-world progress over 2–4 weeks.
What is BMR and TDEE?: BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep organs functioning, breathe, and maintain body temperature. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor, giving your total daily burn including exercise and movement.
What is the difference between Mifflin-St Jeor and Katch-McArdle?: Mifflin-St Jeor uses height, weight, age, and sex. It is the gold standard for the general population. Katch-McArdle uses lean body mass (weight × body fat percentage) and is more accurate for athletic individuals because it accounts for the fact that muscle burns more calories than fat at rest.
What are macronutrients?: Macronutrients are the three main nutrients your body needs in large amounts: Protein (4 calories per gram) — builds muscle and repairs tissue. Carbohydrates (4 calories per gram) — primary energy source for the brain and muscles. Fat (9 calories per gram) — essential for hormone production, vitamin absorption, and cell membrane integrity.
What is a safe rate of weight loss?: A safe and sustainable rate is 0.25–0.5 kg (0.5–1 lb) per week. This requires a daily deficit of 250–500 calories. Losing faster than 1 kg per week often results in muscle loss, nutrient deficiencies, fatigue, and a slower metabolism — making long-term maintenance harder.
Why is my weight loss stalling?: As you lose weight, your BMR decreases because a lighter body burns fewer calories at rest. This is called metabolic adaptation. After losing 5–10% of your body weight, recalculate your TDEE with your new weight and adjust calories accordingly. Also verify your food tracking is accurate — portion estimation errors are very common.
Should I eat the same calories on rest days?: For most people, a consistent daily calorie target is simpler and equally effective. Your body still repairs tissue and replenishes glycogen on rest days, which requires energy. Advanced athletes sometimes use calorie cycling (eating more on training days, less on rest days) but this adds complexity without significant benefit for most people.
How do I choose between diet plans?: Balanced (30/40/30) is a good starting point for general health. Low Carb (40/25/35) suits those with insulin resistance or who feel better with fewer carbs. High Protein (40/30/30) maximises muscle retention during weight loss and is best for active individuals. Keto (25/5/70) is very restrictive but some people find it effective for appetite control.

Medical Disclaimer: This calculator provides estimates for informational purposes only. Results are not a substitute for professional medical or nutritional advice. Consult a registered dietitian or healthcare provider before making significant changes to your diet, especially if you have a medical condition.

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