❤️ Health & Fitness

Losing 5.5 kg over twelve weeks

A 42-year-old man of 82 kg and 178 cm has a basal rate of about 1,728 calories and a lightly active maintenance level near 2,375. Eating 1,875 a day, a 500-calorie deficit, moves the scale about 0.45 kg a week, or 5.5 kg across twelve weeks, bringing him to roughly 76.5 kg. The projection assumes no change in activity and no water-weight noise.

Worked with: BMR Calculator, Calorie Calculator, TDEE Calculator

Getting under a BMI of 25

At 88 kg and 1.72 m the BMI is 29.7, in the overweight band. The weight that gives a BMI of 24.9, the top of the normal range, is 73.7 kg, so 14.3 kg is the distance. Spread over six months that is about 613 calories a day of deficit, which is a large daily change: a slower target of 0.5 kg a week is the more durable route.

Worked with: BMI Calculator, Ideal Weight Calculator

Predicting a half marathon from a 5 km time

A 28:00 5 km runner uses the Riegel formula, time multiplied by the distance ratio raised to 1.06, to set training targets: 128 minutes for a half marathon and 268 minutes for a full one. Those are fitness-based predictions, not guarantees. They assume the mileage is in the legs, which is the part a 5 km time says nothing about.

Worked with: Pace Calculator, Calories Burned Calculator

Dating a pregnancy from the last period

With a last menstrual period on 2 March 2026 and a 28-day cycle, the 40-week due date falls on 7 December 2026. The first trimester ends at the close of week 13, in early June, and the second at the close of week 27, in early September. Dating scans move these dates, so treat the calculator output as the planning figure, not the clinical one.

Worked with: Pregnancy Calculator

A 24-day cycle and a 32-day cycle from the same start date

Two people both record the first day of their last period as 1 June 2025. One runs a regular 24-day cycle and the other a regular 32-day cycle, and both want the fertile window for that cycle.

Inputs: Last period began 1 June 2025. Cycle lengths of 24 days and 32 days.

Result: The 24-day cycle predicts ovulation on 11 June 2025 with a fertile window of 6 to 11 June. The 32-day cycle predicts ovulation on 19 June 2025 with a window of 14 to 19 June.

What it means: The eight-day difference in cycle length moves ovulation by eight days, so a fixed day-14 rule misdates both of these cycles.

Worked with: Ovulation Calculator

A daily calorie target for a 35-year-old woman

A 35-year-old woman weighing 68 kg at 165 cm wants a maintenance figure to work from, and she is honest that most weeks mix desk work with three training sessions.

Inputs: 68 kg, 165 cm, 35 years, activity multipliers of 1.2 for sedentary and 1.55 for moderate.

Result: Mifflin-St Jeor gives a basal rate of 1,375 kcal a day. The sedentary multiplier lifts the target to 1,650 kcal and the moderate multiplier to 2,132 kcal.

What it means: The activity multiplier moves the daily target by 482 kcal, which is larger than the spread between the common BMR equations, so the honest activity estimate matters more than the formula.

Worked with: BMR Calculator, TDEE Calculator, Calorie Calculator

Heart rate zones with no measured maximum

Someone aged 42 with a resting rate of 62 bpm wants training zones and has not had a maximum heart rate test. The age formula and the heart rate reserve method give different answers.

Inputs: Age 42, resting rate 62 bpm, no test result available.

Result: The age formula sets the maximum at 178 bpm. On the percentage method, zone 2 runs from 107 to 125 bpm. The Karvonen method, which starts from the resting rate, puts the same zone at 132 to 143 bpm.

What it means: The two accepted methods disagree by 25 bpm at the bottom of the zone, so pick one and keep using it rather than switching to whichever number suits the session.

Worked with: Heart Rate Zone Calculator