Body measurements
Compare a weight-for-height screening value with a tape-measure estimate of body composition.
BMI CalculatorHealth & Fitness
Health calculators with the method, meaning, and limits in view.
Choose a body measurement, energy, hydration, pregnancy-date, or cycle estimate. Each calculator explains what goes in, what comes out, and when the result may not fit your situation.
- Calculator inputs stay in this tab
- Methods and inputs shown
- Estimates, not diagnoses
Choose by health question
Start with the question you want to answer
These numbers go wrong through misuse far more often than through arithmetic: a screening value read as a diagnosis, an adult cutoff applied to a child, a calendar prediction treated as confirmation. Pick the question first, then read the assumptions the calculator states before acting on what it returns.
Daily energy planning
Estimate resting energy first, then maintenance calories, goal calories, and macro grams.
BMR CalculatorHydration starting point
Estimate a general daily fluid target while keeping weather, activity, and medical limits in context.
Water Intake CalculatorPregnancy & cycle dates
Estimate pregnancy dating or future cycle dates without treating a calendar prediction as confirmation.
Pregnancy Due Date CalculatorTool directory
Health & Fitness tools
Showing 8 of 8 tools
Macro & TDEE Calculator
Compare three resting-energy formulas, estimate TDEE, and convert a selected calorie goal into protein, carbohydrate, and fat grams.
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BMI Calculator
Enter height and weight in metric or imperial units to calculate adult BMI, a general category, and a height-based weight range.
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BMR Calculator
Enter age, sex, height, and weight to estimate resting energy with three formula options and compare TDEE across activity levels.
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Calorie Calculator
Enter age, sex, height, weight, and activity to estimate maintenance and goal calories, with optional protein, carbohydrate, and fat grams.
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Pregnancy Due Date Calculator
Estimate a due date from last period, conception, IVF transfer, or ultrasound information, with gestational timing and key dates.
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Ovulation & Period Tracker
Enter the last period, usual cycle length, and period length to estimate future cycle dates on a monthly calendar.
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Water Intake Calculator
Enter weight, exercise, climate, and selected life-stage adjustments for a general fluid estimate in litres, ounces, and glasses.
Body Fat Percentage Calculator
Enter height, neck, and waist measurements—plus hip measurement for the female formula—to estimate body fat with the U.S. Navy method.
Health calculator guide
Use the estimate as a starting point, not a conclusion
Health calculators can turn a small set of measurements or dates into a useful starting estimate, but the result is only meaningful beside the method that produced it. These tools cover adult BMI and tape-measure body-fat estimates, resting and total daily energy expenditure, calorie and macro planning, a general hydration target, pregnancy dating, and cycle-date awareness. Their formulas use population averages and simplified assumptions. BMI does not directly measure body fat; energy and macro needs change with body weight, activity, health, and life stage; fluid needs vary with climate, food, exercise, medication, pregnancy, breastfeeding, and medical conditions; and pregnancy or ovulation dates remain estimates. Use the number in context and on the calculator's stated population. These tools do not diagnose, treat, prevent, or confirm a medical condition, pregnancy, ovulation, or fertility.
What these tools are designed to help with
Screen body measurements
Use BMI for a weight-for-height screening value or the U.S. Navy circumference method for a separate body-fat estimate. Neither is a diagnosis or complete health assessment.
Estimate energy in stages
Start with resting energy, then add an activity factor to estimate maintenance calories, goal calories, or macro grams. Every stage adds uncertainty.
Set a hydration baseline
Use body weight, exercise, climate, and selected life-stage adjustments for a general starting estimate, while keeping individual fluid needs and restrictions in view.
Estimate dates, not outcomes
Use entered pregnancy or cycle information to estimate dates. Calendar calculations cannot confirm pregnancy, ovulation, fertility, viability, or a future event.
Selection guide
Choose by goal, inputs, and limitation
Similar-looking results often answer different questions. Compare the information each tool needs, the result it produces, and the boundary that matters most before opening it.
Start from the question you are asking
Understanding body measurements?
Use the BMI Calculator for weight relative to height and the Body Fat Percentage Calculator for a separate circumference-based composition estimate.
Estimating daily energy needs?
Use the BMR Calculator for resting energy, the Calorie Calculator for maintenance and goal calories, or the Macro & TDEE Calculator for formula and macro comparisons.
Estimating hydration?
Use the Water Intake Calculator as a general starting point, then consider activity, climate, food, life stage, medication, and any medical fluid guidance.
Tracking pregnancy or cycle dates?
Use the Pregnancy Due Date Calculator for dating estimates and the Ovulation & Period Tracker for calendar awareness, not confirmation or contraception.
Then check what each one needs and what it cannot tell you
Weight-for-height screeningBMI Calculator
- You enter
- Height and weight; metric or imperial units
- You receive
- BMI, adult category, gauge, and weight range for the entered height
- Keep in mind
- BMI does not measure body fat and adult cutoffs do not suit children, pregnancy, or every body type.
Body-composition estimateBody Fat Percentage Calculator
- You enter
- Height, neck, waist, sex-based formula, and hip measurement for the female formula
- You receive
- U.S. Navy circumference estimate and a broad interpretation band
- Keep in mind
- Tape technique and the population-fitted formula can move the result by several percentage points.
Resting energy baselineBMR Calculator
- You enter
- Age, sex, height, weight, formula, and body-fat percentage when Katch-McArdle is selected
- You receive
- Estimated BMR plus TDEE values across activity levels
- Keep in mind
- Prediction equations use population averages; activity bands are not measurements of daily expenditure.
Daily calorie targetCalorie Calculator
- You enter
- Age, sex, height, weight, activity, goal, and macro split
- You receive
- Estimated TDEE, goal calories, and protein, carbohydrate, and fat grams
- Keep in mind
- Outcomes are not guaranteed and the result is not suitable for clinical diets or eating-disorder recovery.
TDEE and macro comparisonMacro & TDEE Calculator
- You enter
- Age, sex, height, weight, activity, goal, formula, macro split, and body fat for Katch-McArdle
- You receive
- BMR, TDEE, goal calories, macro grams, and formula comparison
- Keep in mind
- Macro splits are planning presets, not individualized nutrition prescriptions.
General hydration estimateWater Intake Calculator
- You enter
- Weight, exercise time, climate, selected pregnancy or breastfeeding adjustment, and glass size
- You receive
- Litres, fluid ounces, glasses, and an adjustment breakdown
- Keep in mind
- It cannot account for illness, medication, fluid restrictions, altitude, or individual sweat and sodium losses.
Pregnancy date estimatePregnancy Due Date Calculator
- You enter
- Last period and cycle length, conception date, IVF transfer, or ultrasound dating
- You receive
- Estimated due date, gestational timing, milestones, and key dates
- Keep in mind
- It cannot confirm pregnancy or assess progress; clinical dating takes precedence.
Cycle-date awarenessOvulation & Period Tracker
- You enter
- First day of the last period, usual cycle length, and period length
- You receive
- Predicted ovulation day, fertile window, and upcoming period dates
- Keep in mind
- A fixed calendar model cannot confirm ovulation and becomes less reliable with irregular cycles.
Weight-for-height screening
BMI Calculator
- You enter
- Height and weight; metric or imperial units
- You receive
- BMI, adult category, gauge, and weight range for the entered height
- Keep in mind
- BMI does not measure body fat and adult cutoffs do not suit children, pregnancy, or every body type.
Body-composition estimate
Body Fat Percentage Calculator
- You enter
- Height, neck, waist, sex-based formula, and hip measurement for the female formula
- You receive
- U.S. Navy circumference estimate and a broad interpretation band
- Keep in mind
- Tape technique and the population-fitted formula can move the result by several percentage points.
Resting energy baseline
BMR Calculator
- You enter
- Age, sex, height, weight, formula, and body-fat percentage when Katch-McArdle is selected
- You receive
- Estimated BMR plus TDEE values across activity levels
- Keep in mind
- Prediction equations use population averages; activity bands are not measurements of daily expenditure.
Daily calorie target
Calorie Calculator
- You enter
- Age, sex, height, weight, activity, goal, and macro split
- You receive
- Estimated TDEE, goal calories, and protein, carbohydrate, and fat grams
- Keep in mind
- Outcomes are not guaranteed and the result is not suitable for clinical diets or eating-disorder recovery.
TDEE and macro comparison
Macro & TDEE Calculator
- You enter
- Age, sex, height, weight, activity, goal, formula, macro split, and body fat for Katch-McArdle
- You receive
- BMR, TDEE, goal calories, macro grams, and formula comparison
- Keep in mind
- Macro splits are planning presets, not individualized nutrition prescriptions.
General hydration estimate
Water Intake Calculator
- You enter
- Weight, exercise time, climate, selected pregnancy or breastfeeding adjustment, and glass size
- You receive
- Litres, fluid ounces, glasses, and an adjustment breakdown
- Keep in mind
- It cannot account for illness, medication, fluid restrictions, altitude, or individual sweat and sodium losses.
Pregnancy date estimate
Pregnancy Due Date Calculator
- You enter
- Last period and cycle length, conception date, IVF transfer, or ultrasound dating
- You receive
- Estimated due date, gestational timing, milestones, and key dates
- Keep in mind
- It cannot confirm pregnancy or assess progress; clinical dating takes precedence.
Cycle-date awareness
Ovulation & Period Tracker
- You enter
- First day of the last period, usual cycle length, and period length
- You receive
- Predicted ovulation day, fertile window, and upcoming period dates
- Keep in mind
- A fixed calendar model cannot confirm ovulation and becomes less reliable with irregular cycles.
| Goal | Calculator | Required inputs | Result produced | Important limitation |
|---|---|---|---|---|
| Weight-for-height screening | BMI Calculator | Height and weight; metric or imperial units | BMI, adult category, gauge, and weight range for the entered height | BMI does not measure body fat and adult cutoffs do not suit children, pregnancy, or every body type. |
| Body-composition estimate | Body Fat Percentage Calculator | Height, neck, waist, sex-based formula, and hip measurement for the female formula | U.S. Navy circumference estimate and a broad interpretation band | Tape technique and the population-fitted formula can move the result by several percentage points. |
| Resting energy baseline | BMR Calculator | Age, sex, height, weight, formula, and body-fat percentage when Katch-McArdle is selected | Estimated BMR plus TDEE values across activity levels | Prediction equations use population averages; activity bands are not measurements of daily expenditure. |
| Daily calorie target | Calorie Calculator | Age, sex, height, weight, activity, goal, and macro split | Estimated TDEE, goal calories, and protein, carbohydrate, and fat grams | Outcomes are not guaranteed and the result is not suitable for clinical diets or eating-disorder recovery. |
| TDEE and macro comparison | Macro & TDEE Calculator | Age, sex, height, weight, activity, goal, formula, macro split, and body fat for Katch-McArdle | BMR, TDEE, goal calories, macro grams, and formula comparison | Macro splits are planning presets, not individualized nutrition prescriptions. |
| General hydration estimate | Water Intake Calculator | Weight, exercise time, climate, selected pregnancy or breastfeeding adjustment, and glass size | Litres, fluid ounces, glasses, and an adjustment breakdown | It cannot account for illness, medication, fluid restrictions, altitude, or individual sweat and sodium losses. |
| Pregnancy date estimate | Pregnancy Due Date Calculator | Last period and cycle length, conception date, IVF transfer, or ultrasound dating | Estimated due date, gestational timing, milestones, and key dates | It cannot confirm pregnancy or assess progress; clinical dating takes precedence. |
| Cycle-date awareness | Ovulation & Period Tracker | First day of the last period, usual cycle length, and period length | Predicted ovulation day, fertile window, and upcoming period dates | A fixed calendar model cannot confirm ovulation and becomes less reliable with irregular cycles. |
Practical workflows
Use several estimates without turning them into a prescription
Each workflow keeps the number in its proper role and identifies where context matters more than another calculation.
- 01
Establish a general body baseline
- Use BMI as a quick weight-for-height screening value.Open BMI Calculator
- Add a circumference-based composition estimate if it helps answer a different question.Open Body Fat Percentage Calculator
- Compare trends and context rather than treating either result as a diagnosis.
- 02
Plan around an energy estimate
- Estimate resting energy and compare the available equations.Open BMR Calculator
- Review maintenance calories before selecting a goal.Open Calorie Calculator
- Recalculate when weight, activity, or training volume changes meaningfully.
- 03
Turn maintenance into macros
- Estimate TDEE from the activity level that best matches an average week.Open Macro & TDEE Calculator
- Treat the displayed macro split as a planning preset, not a clinical prescription.
- Use individualized support during pregnancy, breastfeeding, adolescence, or eating-disorder recovery.
- 04
Set a hydration starting point
- Calculate a general baseline from weight and exercise.Open Water Intake Calculator
- Review heat, pregnancy or breastfeeding, and the water already obtained from food and other drinks.
- Follow clinical guidance instead when a condition or medicine affects fluid balance.
- 05
Estimate pregnancy or cycle dates
- Use the available dating method and check the entered date carefully.Open Pregnancy Due Date Calculator
- Use cycle history only for calendar awareness, especially when cycles are regular.Open Ovulation & Period Tracker
- Do not use either estimate to confirm pregnancy, ovulation, fertility, or contraception.
Situations these estimates suit
Each one pairs a calculation with the judgement it cannot make for you.
- Compare BMI with a separate circumference-based body-fat estimate while keeping each method's limitations in view.
- Estimate resting energy first, then review maintenance calories and optional macro planning; the target does not guarantee an outcome.
- Use a hydration result as a starting point and follow individualized guidance when health conditions or medication affect fluid balance.
- Estimate pregnancy or cycle dates while clearly separating calendar predictions from confirmation, diagnosis, or contraception.
Before you calculate
A safe pre-use checklist
- Choose the calculator that matches the question, not the number you hope to see.
- Use current measurements and the same unit system throughout the form.
- Read the formula, population limits, and result note on the calculator page.
- Treat small changes near a category boundary as small changes, not a new diagnosis.
- Recalculate after a meaningful change in weight, activity, cycle pattern, or the information used for pregnancy dating.
- Use professional guidance when symptoms, medication, pregnancy, breastfeeding, age, a medical condition, or eating-disorder history changes what is safe.
When to recalculate: after a meaningful change in the information the formula uses. Repeating the same estimate every day usually adds noise rather than insight.
Quick reference
Terms that are easy to mix up
- BMI
- Body mass index: weight divided by height squared. It is a screening value, not a direct measure of body fat.
- BMR
- Basal metabolic rate: estimated energy used at rest before normal daily activity is added.
- TDEE
- Total daily energy expenditure: BMR multiplied by a broad activity factor.
- Maintenance calories
- An estimated intake that would keep body weight broadly stable if the activity estimate and other assumptions hold.
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