Health & Fitness Calculators
Free health and fitness calculators for BMI, calories, macros, hydration, pregnancy dates, training load and sleep. No sign-up, and every tool shows its formula.
This is the full set of health and fitness calculators on CalcNest. They are built for ordinary decisions rather than clinical diagnosis: working out a calorie target, checking whether a BMI sits inside the healthy band, planning a training week, or estimating a due date and ovulation window. Each page states the formula it uses, the constants behind it (Mifflin-St Jeor for resting energy, WHO BMI bands, IOM pregnancy gain ranges, Karvonen heart-rate zones) and the cases where the estimate stops being reliable. Nothing is sent to a server — the numbers you type stay in your browser, and every result can be copied out in one click.
All 14 health and fitness calculators
BMI Calculator
Body mass index, WHO category and your healthy weight range.
Calorie Calculator
Daily calories to maintain, lose or gain weight (BMR & TDEE).
Macro Calculator
Protein, carb and fat grams for your calorie target and goal.
Water Intake Calculator
How much water to drink per day for your weight and activity.
Due Date Calculator
Estimated due date, current pregnancy week and trimester.
Ovulation Calculator
Predicted ovulation day, fertile window and next period by cycle length.
Pregnancy Weight Gain Calculator
IOM gain range, weekly rate and week-by-week target from your pre-pregnancy BMI.
One Rep Max Calculator
Estimate your 1RM and training percentages from any set.
Sleep Cycle Calculator
Best bedtimes and wake times based on 90-minute cycles.
Ideal Weight Calculator
Devine & Hamwi formulas plus your healthy BMI range.
Body Fat Calculator
Navy tape method: body fat % from three measurements.
Running Pace Calculator
Pace per km/mile, speed, and race time predictions.
Heart Rate Zone Calculator
Your five training zones by the Karvonen method.
Protein Calculator
Daily protein grams by body weight and goal.
How these calculators are built
Each tool is a single static page: the form and the arithmetic run in your browser, so there is no account, no upload and no waiting. The formula block on every page names the constants used, and the FAQ covers the exceptions. If a number disagrees with your supplier or your tape measure, the page tells you which assumption to change rather than hiding it behind a single "result" number.
New calculators are added every week. If something is missing, send a request — reader suggestions decide what gets built next.