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 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). This assumes a standard 28-day cycle. For cycles longer or shorter than 28 days, the due date is adjusted by the difference. Our calculator also supports calculation from a known conception date (adds 266 days) or from a known due date (works backward). An early ultrasound from your doctor is the most accurate method for dating.

How many weeks is a full-term pregnancy?

A full-term pregnancy is 39–40 weeks of gestation. Early term is 37–38 weeks, full term is 39–40 weeks, late term is 41 weeks, and post-term is 42 weeks or beyond. Babies born between 37 and 42 weeks are considered term. Those born before 37 weeks are preterm; those born after 42 weeks are post-term.

What are the three trimesters of pregnancy?

Pregnancy is divided into three trimesters: First Trimester (Weeks 1–13): The embryo develops all major organs. Morning sickness, fatigue, and breast tenderness are common. The risk of miscarriage is highest in this period. Second Trimester (Weeks 14–27): Often called the "golden period." Most women feel better, the belly becomes visible, and the baby begins to move. Anatomy scans are scheduled around week 20. Third Trimester (Weeks 28–40+): Rapid growth phase. The baby gains most of its weight. The lungs mature in preparation for birth.

How accurate is a due date from LMP?

A due date from LMP is an estimate — only about 5% of babies are born on their exact due date. The LMP method is most accurate for women with a regular 28-day cycle. Women with irregular periods or longer/shorter cycles may find the conception date method more accurate. The gold standard for dating is an early ultrasound (before 13 weeks), which measures the baby's crown-rump length to calculate gestational age.

Can my due date change after an ultrasound?

Yes. It is common for the due date to be adjusted after a first-trimester ultrasound. If the measured size of the baby differs significantly (typically by more than 5–7 days) from the LMP-based date, your healthcare provider may update your estimated due date. The ultrasound date is considered more reliable and becomes the official due date.

What is the due date if I have an irregular menstrual cycle?

If your cycle is irregular, the LMP method may be inaccurate. If you know your typical cycle length, enter it in our cycle length field for a more personalized estimate. Alternatively, if you know your conception date (or had IVF), use the Conception/IVF mode for greater accuracy. An early ultrasound from your healthcare provider is the most reliable method for dating a pregnancy with irregular cycles.

How is the due date calculated for IVF?

For IVF with a Day 3 embryo transfer: add 263 days to the egg retrieval date (266 days of gestation minus 3 days). For IVF with a Day 5 (blastocyst) transfer: add 261 days to the egg retrieval date (266 days minus 5 days). Alternatively, enter the egg retrieval date in our calculator's Conception/IVF mode, then adjust manually by subtracting 3 or 5 days depending on your transfer day. Always confirm your due date with your fertility specialist.

What happens if I go past my due date?

Going past your due date — especially by 1–2 weeks — is very common, particularly for first-time mothers. Your doctor will monitor you and your baby closely with non-stress tests and ultrasounds. If you reach 41–42 weeks with no signs of labor, your doctor may discuss inducing labor to reduce risks. Never attempt to induce labor on your own without medical guidance.

What is viability in pregnancy?

Viability refers to the gestational age at which a premature baby has a reasonable chance of survival with medical support. This is generally considered to begin around 22–24 weeks of gestation. At 24 weeks, survival rates are approximately 40–70% with intensive neonatal care; at 28 weeks, survival exceeds 90%. Before 22 weeks, the lungs and vital organs are not sufficiently developed for survival outside the womb.

Is this pregnancy calculator a substitute for medical advice?

No. This calculator provides estimates for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Pregnancy due dates are estimates — only a healthcare provider using a combination of your menstrual history, physical examination, and ultrasound can give you a confirmed due date and monitor the health of your pregnancy. Always consult a qualified obstetrician, midwife, or healthcare professional for guidance on your pregnancy.

Back to Health Calculators

Pregnancy Due Date Calculator

Find your estimated due date, track your trimester progress, discover key milestones, and explore your week-by-week pregnancy journey.

LMP · Conception · IVFCycle AdjustmentKey MilestonesBaby ZodiacWeek-by-Week Guide

For informational use only. This calculator provides estimates. Always consult your healthcare provider for your official due date and pregnancy guidance.

First Day of Last Menstrual Period

Average Cycle Length: 28 days

20 days28 days (standard)45 days

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Three Ways to Calculate Your Due Date

📅

From Last Menstrual Period

Enter the first day of your last period. The calculator uses Naegele's Rule (LMP + 280 days). Adjust the cycle length slider for cycles other than 28 days — this is the most important accuracy improvement over basic calculators.

🎯

From a Known Due Date

If your doctor has already given you a due date from an ultrasound, enter it here to see your full timeline: estimated conception date, gestational age today, trimester, and milestone dates.

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From Conception / IVF

For known conception dates or IVF: enter the conception date and the calculator adds 266 days (38 weeks of true gestation). For IVF Day 5 blastocyst transfer, subtract 5 days from your egg retrieval date before entering.

Understanding the Three Trimesters

1st Trimester

Weeks 1–13

•All major organs begin forming
•Heart starts beating (week 6)
•Highest risk period for miscarriage
•Common: nausea, fatigue, breast tenderness
•Nuchal translucency scan (weeks 11–13)

2nd Trimester

Weeks 14–27

•Often called the "golden period"
•Morning sickness typically subsides
•Baby's movements felt (quickening)
•Anatomy ultrasound (weeks 18–22)
•Viability milestone reached (week 24)

3rd Trimester

Weeks 28–40+

•Rapid baby weight gain
•Lungs maturing for birth
•Braxton Hicks contractions increase
•GBS screening (week 36)
•Full term at 39 weeks

Frequently Asked Questions

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