Know your body's numbers.
Your body runs on numbers — BMI, TDEE, sleep cycles, hydration, heart-rate zones — but those numbers only help when you know what to do with them. Each Health calculator on CalcBold uses the published clinical formula (WHO, NIH, Mifflin-St Jeor) and pairs the result with an AI explanation in plain English. Educational only — never a substitute for your doctor.
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Top health tools
- #1 Most-searched
BMI Calculator
Calculate your body mass index instantly in metric or imperial units. See your WHO category, healthy weight range, BMI Prime, and an AI insight for your result.
15M+/month
- #2
Calorie / TDEE Calculator
Mifflin-St Jeor BMR, your Total Daily Energy Expenditure, and a complete macro split (protein · fat · carbs) for your weight-loss, maintenance, or muscle-gain goal.
5M+/month
- #3
Pregnancy Due Date Calculator
Drop your last menstrual period (LMP) or conception date — get the estimated due date, current gestational age in weeks/days, trimester, and the full-term window. Cycle-length adjustment included.
4M+/month
Try it live
BMI Calculator — instant
The health tool with the highest monthly demand. Run it here, then open the full version for AI insight, scenarios, and embed code.
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Every health calculator
32 live
Body Composition
13 tools- BMI Hot
BMI Calculator
Calculate your body mass index instantly in metric or imperial units. See your WHO category, healthy weight range, BMI Prime, and an AI insight for your result.
15M+/month - Body Fat New
Body Fat Calculator
The most-validated tape-only body fat estimate. Drop your waist, neck, height, and (women) hip — get body fat percentage with category, accuracy band, and where you sit on the fitness range.
2M+/month - Ideal Weight New
Ideal Weight Calculator
Four classic ideal-body-weight formulas (Devine, Hamwi, Robinson, Miller) plus the BMI healthy-range method. None is 'the right answer' — together they give a healthy weight range, not a single target.
2M+/month - GLP-1 Lifetime New
GLP-1 (Ozempic / Wegovy) Lifetime Cost
Total drug cost adjusted by insurance + comorbidity offset. Weight-loss + post-discontinuation regain. Compare lifestyle vs bariatric paths.
600K/month - Bio Age New
Biological Age Calculator
Drop your chronological age and 9 lifestyle inputs. Calculator returns your biological age (chronological + per-factor year adjustment), the gap between your calendar and your biology, the single largest factor moving the gap, and 3 lever rows showing exactly how many years quitting smoking, hitting WHO exercise target, or trimming alcohol would recover. Anchored on Doll & Peto 2004, Lee 2012, Kvaavik 2010, Berkeley HEI 2023 — well-cited longevity research, not horoscope numerology.
270K+/month - Quit Savings New
Smoking Quit Savings Calculator
Drop your cigs/day, price per pack, years already smoked, projection horizon, and expected investment return. Calculator returns annual spend, sunk cost on cigarettes already smoked, future spend if you continue, the opportunity cost if that future money compounded in the S&P 500 at the long-run real return of ~7% (Damodaran data), pack-years (the standard exposure metric), estimated lifespan recoverable (anchored on Doll & Peto 2004 BMJ ~10 yr lifespan loss + Surgeon General 2020 cardiovascular reversal data), and a cost-per-recovered-life-year framing.
180K+/month - Eldercare Lifetime New
Eldercare Lifetime Cost Calculator
Monthly cost by care level + state, lifetime NPV with caregiver opportunity cost, Medicaid 5-yr lookback exposure, 10-yr asset depletion counterfactual.
180K/month - Chronic Illness Cost New
Chronic Illness Lifetime Cost (T2D / HTN / CKD)
30-year lifetime medical cost projection by condition. Lifestyle adherence × management quality multiplier. Productivity loss + premature death NPV.
85K/month - Meditation Impact New
Meditation Impact Calculator
Drop your minutes per day, days per week, weeks of consistent practice, and current stress level (1-10). Calculator returns your weekly meditation dose, lifetime hours invested, the percentage of research-grade effect you’ve realized, projected stress level after the practice ramps in, sleep-quality lift, estimated cortisol reduction, and biological-age benefit. Anchored on Goyal 2014 (JAMA Intern Med, g≈0.30 stress effect), Pascoe 2017 (cortisol drop), and Black 2015 (sleep). Time-ramp built in: 0% effect at week 0, 80% at week 8, 100% at week 24+.
65K+/month - CGM Non-Diabetic New
CGM Non-Diabetic ROI Calculator
Behavior-change value vs subscription cost. T2D prevention probability impact. Buy-3-months-then-decide strategy.
55K/month - A1c New
A1c Calculator
Convert A1c (HbA1c) to estimated average glucose and back, with ADA 2025 diabetes categories, mg/dL ↔ mmol/L unit toggle, and decision-score gauge.
27.1K/month · $13 CPC - Puppy Weight New
Puppy Weight Predictor
Drop your puppy's current weight, age in weeks, and breed class — get the predicted adult weight with a ±15% confidence band, growth-curve projection through 24 months, and life-stage feeding guidance.
18.1K/month · $4.62 CPC - Treadmill Calorie New
Treadmill Calorie Calculator
Calculate exact calories burned on a treadmill using the ACSM walking + running metabolic equations. Speed, incline, weight, and duration drive the burn rate; age supplies an HR-zone overlay.
8.1K/month · $4.92 CPC
Nutrition & Hydration
7 tools- Calories Hot
Calorie / TDEE Calculator
Mifflin-St Jeor BMR, your Total Daily Energy Expenditure, and a complete macro split (protein · fat · carbs) for your weight-loss, maintenance, or muscle-gain goal.
5M+/month - Water New
Water Intake Calculator
Compute your daily water target from bodyweight (35 ml/kg base), activity level, climate, and life-stage adjustments (pregnancy, breastfeeding). Output in liters, US cups, and 250 ml glasses.
2M+/month - Macros New
Macro Calculator
Daily calorie target plus the exact protein / fat / carbs split (in grams) for cutting, maintaining, or bulking — adapted to your diet preference (balanced · high-protein · keto · mediterranean). Goal-aware splits, not a fixed 40/30/30.
1.2M+/month - Protein New
Protein Intake Calculator
Drop your bodyweight, goal, and meal frequency — get your daily protein target in grams plus per-meal breakdown. Goals span sedentary maintenance (0.8 g/kg) through cutting (2.4 g/kg).
1M+/month - Macros Cut/Bulk New
Macros Cutting / Bulking Calculator
Drop your weight, height, age, sex, activity level, goal (cut, maintain, bulk) and aggressiveness. Calculator returns Mifflin-St Jeor BMR, TDEE with ACSM 2018 activity factors, target calories with the goal modifier applied, ISSN 2017-anchored protein target (1.0-1.4 g/lb cuts, 0.8-1.0 bulks), fat (28% cuts / 22% bulks of kcal — above the hormonal-floor minimum), carbs filling the remainder, and the expected weekly weight change at that deficit or surplus.
165K+/month - Alcohol Cost New
Alcohol Cost Calculator
Drop your weekly drinks, price per drink, projection horizon, and expected investment return. Calculator returns annual and lifetime spend, total alcohol calories converted to equivalent pounds of body fat, biological-age years added (anchored on Sheron 2018 + GBD 2018), and the opportunity cost if the same money compounded in the S&P 500 at the long-run real return of ~7% (Damodaran data). Plus an explicit lever row showing recoverable dollars and bio-age years from dropping to ≤7 drinks/wk.
95K+/month - Nutrient Density New
Nutrient Density Calculator
Drop your daily vegetable, fruit, whole-grain, lean-protein, ultra-processed, and sugary-drink counts. Calculator returns a 0-100 nutrient-density score using a Drewnowski NRF 9.3 simplified self-assessment framework — qualifying contributors (vegetables, fruits, whole grains, lean protein, dairy/calcium) minus disqualifying loads (ultra-processed share, sugary drinks). Plus your population percentile vs the NHANES 2018 American adult median (~45-50), likely deficiency risks, and the highest-leverage single-change lever (typically +2 veg + 1 fruit/day = +15-20 points).
45K+/month
Fitness & Training
8 tools- Sleep Hot
Sleep Cycle Calculator
Pick a wake time and we compute bedtime options in 90-minute sleep cycles — or flip the mode to find ideal wake times from a bedtime. Backed by 14-minute average sleep latency.
1.5M+/month - HR Zones Hot
Heart Rate Zone Calculator
Drop your age (and optionally resting heart rate) — get max HR plus the 5 training zones (Z1 recovery → Z5 VO2 max). Three formulas: Tanaka (default, accurate), Fox (220−age, legacy), and Karvonen (heart-rate-reserve method, athletes' choice).
800K+/month - Pace New
Running Pace Calculator
Pick any 2 of distance, time, or pace — the calculator solves for the third. Compute pace mode adds 5K · 10K · half · marathon time predictions via the Riegel formula. Metric / imperial toggle.
700K+/month - 1RM New
One-Rep Max Calculator
Estimate your true 1RM from any sub-maximal set using 4 validated formulas (Epley · Brzycki · Lombardi · O'Conner) — then get the exact work weight for every %-of-1RM training zone (5×5 strength, 8×3 hypertrophy, max-singles).
150K+/month - Sleep Debt New
Sleep Debt Calculator
Drop your target sleep, your honest average, and how long you have been running short. Calculator returns total sleep debt, the cognitive deficit equivalent expressed as Blood Alcohol Concentration (Dawson & Reid 1997 equivalence), recovery time at your catch-up rate, weekend-only recovery weeks, and the annualized hours of life-functioning you are losing if the pattern continues. Built on van Dongen 2003 chronic-restriction data — two weeks at 6 hrs/night ≈ 24 hrs of acute deprivation.
120K+/month - VO2max New
VO2max Target Calculator
Pick a field test (Cooper 12-min run, Uth-Sørensen HR-ratio, or Burr 6-min walk) and the calculator returns your estimated VO2max in mL/kg/min, your gap vs the ACSM 2022 age- and sex-adjusted population median, your fitness percentile, your fitness category from POOR to SUPERIOR, and the mortality-hazard ratio vs the top 25% from Mandsager 2018 (JAMA). VO2max is the single strongest cardiorespiratory fitness biomarker available without a metabolic-cart lab and one of the highest-leverage longevity inputs you can move with 12-week training blocks.
85K+/month - Wearable Stack ROI New
Wearable Stack ROI (Oura + Whoop + Watch)
Redundancy detection across multi-device stacks. Recommended pruned stack. Monthly spend vs validated benefit by use case.
60K/month - Exercise Equivalent New
Exercise Equivalent Calculator
Drop a calorie count and your bodyweight in pounds. Calculator returns the minutes of walking, running, cycling, swimming, elliptical, rowing, dancing, hiking, yoga, and strength training equivalent to those calories — using the Ainsworth 2011 Compendium of Physical Activities MET tables. Honest framing built in: Pollock 2011 evidence that diet beats exercise for weight loss above ~300 kcal/day, so use the calculator as a portion-perspective tool, not a permission slip.
55K+/month
Pregnancy & Cycles
4 tools- Due Date Hot
Pregnancy Due Date Calculator
Drop your last menstrual period (LMP) or conception date — get the estimated due date, current gestational age in weeks/days, trimester, and the full-term window. Cycle-length adjustment included.
4M+/month - Ovulation Hot
Ovulation Calculator
Predict your most-likely ovulation date and the 6-day fertile window from the first day of your last period (LMP) and your cycle length. Sister calc to Pregnancy Due Date.
3M+/month - Pregnancy Week New
Pregnancy Week-by-Week Calculator
Find your exact gestational age (weeks + days) from LMP, conception date, known due date, or first-trimester ultrasound CRL. Plus a complete week-by-week milestones reference (size, length, common symptoms, key appointments) — non-medical, evidence-aligned.
2M+/month - IVF Total Cost New
IVF Total Cost Calculator
Per-cycle cost by state, expected cycles to live birth based on age, insurance offset, donor-egg / PGT-A adders, and cumulative success probability.
320K/month
Sources we cite
Where the health numbers come from
WHO BMI thresholds · Mifflin-St Jeor TDEE · 90-min sleep cycle research · Navy body-fat method
Frequently Asked Questions
The most common questions we get about this calculator — each answer is kept under 60 words so you can scan.
Are these health calculators medical advice?
No. CalcBold health tools are educational. They use the same formulas your doctor's office uses (BMI from WHO, TDEE from Mifflin-St Jeor, etc.), but they cannot account for medications, conditions, body composition, pregnancy, or context only a clinician can assess. Use them to inform a conversation, not replace one.Which formulas do you use, and why those?
BMI: WHO standard (kg/m²). TDEE/calories: Mifflin-St Jeor (most accurate for general population per peer-reviewed comparisons). Body fat: Navy method (tape-measure, no scale needed). Sleep: 90-minute cycle model from sleep-research literature. Each calculator page links the source.How private is my health data?
All math runs in your browser — height, weight, age, cycle dates never leave your device. The only outbound call is to our AI proxy to generate the insight paragraph, and that request is not logged. There are no accounts, no health profiles, no third-party trackers inside the calculator surface.Why do some results feel off — am I really overweight?
BMI is a population-level signal, not a personal verdict. Athletes with high muscle mass routinely score 'overweight'; older adults can score 'normal' while carrying unhealthy visceral fat. Pair BMI with body-fat percentage and waist measurement for a fuller picture. The calculator says so explicitly when your inputs suggest an edge case.