What each tool does
BMI Calculator
BMI is weight in kilograms divided by height in metres squared (or 703 × pounds ÷ inches squared). For adults the WHO classes 18.5–24.9 as healthy, 25–29.9 as overweight and 30 or more as obese. For people of South Asian and other Asian backgrounds, NICE and the WHO suggest lower cut-offs: overweight from 23 and obesity from 27.5.
EDD Calculator (Due Date)
The EDD (expected date of delivery), or due date, is estimated as 280 days (40 weeks) after the first day of the last menstrual period (LMP), which is Naegele's rule: add 1 year, subtract 3 months and add 7 days to the LMP. Cycles longer or shorter than 28 days shift the date by the difference. Only about 4–5% of babies arrive on the due date itself; most are born within two weeks either side. An early ultrasound gives a more accurate date.
Calorie Calculator
Daily calorie needs are estimated by working out basal metabolic rate (BMR) with the Mifflin-St Jeor equation, then multiplying by an activity factor from 1.2 (desk job) to 1.9 (very active). For gradual weight loss, many guidelines suggest eating about 500 kcal a day below that figure, and not going below about 1,200 kcal (women) or 1,500 kcal (men) without medical advice.
Ovulation Calculator
Ovulation usually happens about 14 days before the next period starts, so in a 28-day cycle it falls around day 14. The fertile window is the five days before ovulation plus ovulation day itself, because sperm can survive up to five days. These dates are estimates; cycles vary, and ovulation tests or tracking temperature give a closer picture.
Blood Pressure Checker
Normal adult blood pressure is below 120/80 mmHg. Under the American Heart Association categories, 120–129 systolic with diastolic under 80 is elevated, 130–139 or 80–89 is stage 1 hypertension, 140/90 or higher is stage 2, and above 180/120 is a hypertensive crisis needing urgent care. UK NICE guidance diagnoses hypertension from a clinic reading of 140/90 or higher confirmed by home or ambulatory readings of 135/85 or higher.
eGFR Calculator
eGFR estimates how well the kidneys filter blood, in mL/min/1.73 m². The CKD-EPI 2021 equation uses serum creatinine, age and sex without a race coefficient. An eGFR of 90 or above is normal; 60–89 is mildly reduced; below 60 for three months or more indicates chronic kidney disease (stages G3a to G5, with G5 below 15 meaning kidney failure).
HbA1c Calculator
HbA1c reflects average blood glucose over about three months. To convert, IFCC mmol/mol = (HbA1c % − 2.15) × 10.929, so 6.5% equals 48 mmol/mol. Estimated average glucose (eAG) in mg/dL = 28.7 × HbA1c % − 46.7, so 7% corresponds to about 154 mg/dL (8.6 mmol/L). The ADA classes below 5.7% as normal, 5.7–6.4% as prediabetes and 6.5% (48 mmol/mol) or above as diabetes.
Blood Sugar Converter
To convert blood glucose from mg/dL to mmol/L, divide by 18 (more precisely 18.016). To convert mmol/L to mg/dL, multiply by 18. So 100 mg/dL is 5.6 mmol/L and 7.0 mmol/L is 126 mg/dL. A fasting glucose below 100 mg/dL (5.6 mmol/L) is normal, 100–125 mg/dL is impaired fasting glucose under ADA criteria, and 126 mg/dL (7.0 mmol/L) or more suggests diabetes.
Lab Unit Converter
Lab results are converted with a fixed factor for each test. Cholesterol in mg/dL ÷ 38.67 = mmol/L; triglycerides ÷ 88.57; glucose ÷ 18.02; creatinine in mg/dL × 88.4 = µmol/L; uric acid × 59.48; bilirubin × 17.1; vitamin D in ng/mL × 2.496 = nmol/L; calcium in mg/dL ÷ 4.008 = mmol/L; and haemoglobin in g/dL × 10 = g/L.
Body Fat Calculator
The US Navy method estimates body fat from height and neck and waist circumference (plus hip for women). For men: %fat = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76, in inches. Typical ranges from the American Council on Exercise are 14–17% (fitness) and 18–24% (average) for men, and 21–24% and 25–31% for women. It is usually within about 3–4% of lab methods.
Safe Period Calculator
No day of the cycle is completely safe, but the calendar method estimates the fertile days to avoid. Using at least six months of cycle records, the first fertile day is the shortest cycle length minus 18, and the last fertile day is the longest cycle length minus 11. If every cycle is 26 to 32 days long, the Standard Days Method treats days 8 to 19 as fertile. With typical use, about 12 in 100 women using the Standard Days Method become pregnant in a year.