Health & Lifestyle

The standard method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). Most pregnancies are dated from the LMP even though conception usually occurs around 2 weeks later. An ultrasound scan (usually at 8–14 weeks) gives a more accurate due date by measuring the fetus. The CalcHub pregnancy calculator uses both methods.

The NHS recommends not drinking more than 14 units per week regularly, spreading consumption over 3+ days, and having several alcohol-free days each week. One unit equals 10ml of pure alcohol. A pint of 4% beer is 2.3 units; a 175ml glass of 13% wine is 2.3 units; a single 25ml measure of 40% spirits is 1 unit. The CalcHub alcohol unit calculator converts drinks to units.

Waist circumference is a useful health indicator alongside BMI. For men: below 94cm (37 inches) is low risk; 94–102cm is increased risk; above 102cm is high risk. For women: below 80cm (31.5 inches) is low risk; 80–88cm is increased risk; above 88cm is high risk. These NHS thresholds are lower for South Asian, Chinese and Black African or Caribbean family backgrounds.

NHS Health Checks are offered every 5 years to adults in England aged 40–74 who do not already have cardiovascular disease, diabetes, kidney disease or certain other conditions. They assess your risk of heart disease, stroke, diabetes and kidney disease and are free. Contact your GP surgery or local council to book. Wales, Scotland and Northern Ireland have their own preventive health programmes.

There is no single "ideal weight" — healthy ranges are usually expressed as a BMI of 18.5–24.9 for adults. The CalcHub ideal weight calculator shows the weight range that falls within the healthy BMI band for your height, plus alternative estimates using the Devine, Hamwi and Robinson formulas used clinically. These formulas are approximations; body composition (muscle vs fat) is also important.

The NHS recommends eating at least 5 portions of fruit and vegetables per day (roughly 400g total). A portion is 80g of most fruits or vegetables, 30g of dried fruit, or 150ml of unsweetened juice (one portion maximum). Potatoes do not count. Eating a variety of colours maximises different vitamins, minerals and phytonutrients. Beans and pulses count once regardless of how much you eat.

NHS Choices (nhs.uk) is the primary authoritative source for UK health information. NICE (nice.org.uk) publishes clinical guidelines. Public Health England (part of UKHSA) publishes population health data. The CalcHub Health & Lifestyle calculators translate these guidelines into personalised numbers — always follow your GP's advice for individual health decisions.