Health and fitness calculators

Calories In, Calories Out: The Data Behind Weight Change

Weight change follows a single equation: calories consumed minus calories expended. Everything else — macros, meal timing, food quality — affects compliance, not thermodynamics. If you want to know your number, start with BMR (what you burn at rest) and TDEE (what you burn with activity factored in). The TDEE calculator gives you both plus calorie targets for cutting, maintaining, or bulking.

Worked example: A 200 lb male, 5'10", 30 years old, exercising 3 days per week has a TDEE of roughly 2,900 calories. To lose 1 lb per week (3,500 calorie deficit), eat 2,400 calories daily. To gain muscle at 0.5 lb per week, eat 3,150 calories daily. These targets give you a starting point, not a prescription — adjust after two weeks of consistent tracking.

Worked example: A 180 lb person walking at 3 mph for 60 minutes burns roughly 285 calories (MET value of 3.5 × 81.6 kg × 1 hour). The same person jogging at 5 mph for 30 minutes burns about 345 calories. The calories burned calculator covers 40+ activities from walking and running to cycling, swimming, weightlifting, and yoga — each using MET values from the Compendium of Physical Activities, which is the standard reference for exercise science.

BMI: Useful Data Point, Not a Diagnosis

BMI divides your weight in kilograms by your height in meters squared. It correlates with body fat at a population level but tells you nothing about an individual's body composition. The BMI calculator gives you your number and category with a gauge visualization, but interpret it with context.

Limitation example: A 5'10" male at 190 lb with 12% body fat has a BMI of 27.3 — technically overweight. The same height at 160 lb with 25% body fat has a BMI of 23 — normal. The "overweight" person is carrying more muscle and less fat. BMI cannot tell the difference. This is why the calculator is useful as a screening tool, not a verdict. If you carry significant muscle, treat the BMI number as a baseline and focus on other metrics like waist circumference or body fat percentage for a more accurate picture.

Sleep Cycles, Hydration, and Due Dates

These calculators answer specific practical questions with no room for guesswork.

Sleep. The average sleep cycle lasts 90 minutes. Waking up mid-cycle leaves you groggy because you interrupt REM or deep sleep. Waking at the end of a cycle leaves you refreshed. The sleep calculator works backward from your wake time: if you need to be up at 6:30 AM, aim for sleep at 11:00 PM (5 cycles) or 12:30 AM (4 cycles). Or if you are going to bed now, it tells you the best alarm times for the next 4.5 to 9 hours in 90-minute increments.

Hydration. The old "8 glasses per day" rule is a catchall that ignores body size, activity, and climate. A 150 lb person in a temperate climate who exercises lightly needs roughly 90 ounces of water daily (0.6 oz per lb). A 200 lb person who exercises heavily in a hot climate needs closer to 140 ounces. The water intake calculator adjusts for weight, activity level, and climate — and gives an hourly drinking schedule so you pace it through the day instead of chugging at night.

Due dates. Pregnancy due dates are calculated as 40 weeks from the first day of the last menstrual period, or 38 weeks from conception. The due date calculator supports LMP, conception date, and IVF transfer date — and also shows current week and trimester. Note that only about 5% of babies arrive on their exact due date; the tool gives you a target window, not a guarantee.

Frequently Asked Questions

How many calories do I burn walking 10,000 steps?

10,000 steps is roughly 5 miles depending on stride length. A 160 lb person burns about 400 to 500 calories walking that distance at a moderate pace (3 mph). Heavier people burn more because moving more mass requires more energy. The calories burned calculator gives a more precise estimate based on your exact weight and pace.

What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest to keep your heart, lungs, and organs running. TDEE (Total Daily Energy Expenditure) is BMR plus all activity — walking, exercise, fidgeting, digesting food. Your TDEE determines whether you lose, maintain, or gain weight. The TDEE calculator shows both numbers.

Is BMI accurate for athletes and muscular people?

No. BMI does not distinguish between muscle and fat. A muscular athlete can have a BMI in the "overweight" or "obese" range while having very low body fat. Use BMI as a rough screening tool, and rely on body fat percentage, waist circumference, or how your clothes fit for individual assessment. The BMI calculator includes a clear limitation note on this.

How much water should I really drink per day?

The general guideline is 0.5 to 0.7 ounces per pound of body weight, adjusted for activity and climate. A sedentary 150 lb person in mild weather needs about 75 to 105 ounces. That same person doing an hour of intense exercise in summer heat needs closer to 120 to 150 ounces. The water intake calculator factors all of this in.

How does the sleep calculator determine the best bedtime?

It works backward from your wake-up time in 90-minute sleep cycles. If you need to wake at 7:00 AM, falling asleep at 11:30 PM gives 5 full cycles (7.5 hours) and you wake between cycles instead of mid-cycle. Going to sleep at 10:00 PM would mean waking mid-cycle at the 9-hour mark, which leaves you groggier than 7.5 hours would. The sleep calculator does all this timing for you.

Related categories

• Math calculators & converters
• Finance tools for freelancers
• Freelancer business tools