Health tools
BAC Calculator
Free BAC calculator using the Widmark formula — a clearly-labeled educational estimate, not a tool for deciding whether it's safe to drive. If you've been drinking, the only safe choice is not to drive, regardless of what any calculator shows.
BMI Calculator
Calculate your Body Mass Index (BMI) from height and weight, and see where you fall on the standard weight range.
BMR Calculator
Free BMR calculator with a choice of three formulas — Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle for people who know their body fat percentage — not just the one formula most calculators default to.
Body Fat Calculator
Free body fat calculator using the US Navy circumference method — with a plausibility check that flags results outside the physiologically typical range, instead of confidently showing a number that may be unreliable for your body shape.
Body Surface Area Calculator
Free body surface area calculator using the Mosteller formula — the version most commonly cited in clinical references for its simplicity and accuracy.
Body Type Calculator
Free body frame size calculator using an actual measurement (height-to-wrist ratio) instead of a self-reported body type quiz — small, medium, or large frame, based on bone structure.
Caffeine Intake Calculator
Track today's caffeine from coffee, tea, energy drinks, and soda — checked against both the flat FDA limit and a more personalized, weight-based limit.
Calorie Calculator
Free calorie calculator that turns your maintenance calories (TDEE) into a daily target for losing, maintaining, or gaining weight, using the real ~7,700 calorie-per-kilogram-of-fat rule for the rate you choose.
Calories Burned Calculator
Free calories burned calculator using standard MET (metabolic equivalent) values across 12 common activities — from walking to weight training — based on your actual weight and duration.
Creatine Dosage Calculator
Free creatine dosage calculator using ISSN (International Society of Sports Nutrition) guidelines — see your exact loading-phase and maintenance-phase doses by body weight, plus how much longer it takes to saturate your muscles if you skip loading.
Fiber Intake Calculator
Track today's fiber from common foods against your age- and sex-based daily target — no account, no paywall, no ads.
GFR Calculator
Free eGFR calculator using the 2021 CKD-EPI race-free equation — the current clinical standard, which removed the race coefficient used in older versions — with CKD stage classification.
GLP-1 Cost Calculator
Compare official manufacturer-published GLP-1 prices (Wegovy, Ozempic, Mounjaro, Zepbound) across cash-pay, insurance-with-savings-card, and Medicare Bridge — no lead form, no referral to any provider.
Healthy Weight Calculator
Free healthy weight calculator that gives a BMI-based weight range for your height — a single input, a clear range, and an honest note about what BMI does and doesn't capture.
Ideal Weight Calculator
Free ideal weight calculator showing all four classic formulas (Devine, Robinson, Miller, Hamwi) side by side — not just one number, so you can see how much these decades-old formulas actually disagree.
Lean Body Mass Calculator
Free lean body mass calculator using the Boer formula — a quick estimate of your fat-free mass from height, weight, and sex, no body fat percentage measurement required.
Macro Calculator
Free macro calculator that shows carbohydrate, protein, and fat targets all at once from your TDEE — instead of the separate carb, protein, and fat calculators most sites split into three different pages.
Menopause Age Estimator
A menopause age range estimator built to be honest about its own limits — combines your mother's menopause timing and smoking history with published averages to show a plausible range, never a false-precision single year.
One Rep Max Calculator
Free one rep max calculator showing both the Epley and Brzycki formulas side by side, plus a full training percentage table (60-95% of 1RM) — not just a single estimated max.
Ovulation Calculator
Free ovulation calculator that estimates your fertile window and ovulation date from your last period and cycle length — the same underlying calculation as a conception calculator, in one tool.
Pace Calculator
Free running pace calculator that solves for pace, time, or distance — whichever one you don't know — and shows results in both min/km and min/mile at once.
Period Calculator
Free period calculator that predicts your next 6 cycles from your last period date and average cycle length — not just the next one.
Pregnancy Calculator
Free pregnancy calculator that works both directions — from your last period to a due date, or backward from a known due date to your estimated conception window — with current gestational age and trimester shown either way.
Pregnancy Weight Gain Calculator
Free pregnancy weight gain calculator using the US Institute of Medicine's 2009 guidelines — your recommended total weight gain range based on your pre-pregnancy BMI category.
Protein Calculator
Free protein calculator using the 2026-updated USDA/HHS activity-based range — no account, no paywall, with a running tally from 6 common high-protein foods.
Sleep Cycle Calculator
Free sleep cycle calculator based on 90-minute sleep cycles — enter a wake-up time to see bedtime options, or a bedtime to see wake-up options, for waking up at the end of a full cycle.
Target Heart Rate Calculator
Free target heart rate calculator using the Karvonen method (heart rate reserve), with a choice between the traditional 220-minus-age formula and the more accurate Tanaka formula for max heart rate.
TDEE Calculator
Free TDEE calculator that shows exactly how much a wrong activity-level pick can cost you — up to 250 calories/day between adjacent levels — instead of just outputting a number with no context.
From the blog
You don't need to load creatine — skipping it just trades a week for a month
The ISSN's own guidelines back both approaches: loading saturates muscle creatine stores in about a week, skipping it reaches the same place in about a month.
2026-09-08 No calculator can tell you your exact menopause age — here's what the research can actually tell you
Menopause age predictors that promise a precise number overstate what the science supports. A mother's timing and smoking history shift the odds — they don't pin down a year.
2026-09-08 MyFitnessPal Puts Fiber Tracking Behind a $79.99/Year Paywall. This Calculator Doesn't Have One.
Most nutrition apps show calories for free and bury fiber a few taps deep — or lock it behind Premium entirely. With "fibermaxxing" pushing more people to actually track fiber, we built a calculator that only does that one thing, for free.
2026-09-03 How Much Protein Do You Actually Need? The 2026 USDA Guidelines Changed the Answer
The 2025–2030 USDA/HHS Dietary Guidelines, updated in January 2026, raised the general protein range to 1.2–1.6 g/kg — well above the old 0.8 g/kg minimum most calculators still show. Here's the updated math, and a free calculator with no paywall.
2026-09-03 Waking up mid-cycle is why 8 hours can feel worse than 7.5 — this calculator works backward from full cycles, not round numbers
Picking a bedtime by rounding to the nearest half hour ignores the 90-minute sleep cycle entirely. This calculator works from full cycles instead.
2026-09-02 The FDA's 400mg caffeine limit is an average for a 160lb adult — not a rule for everyone
A flat daily limit doesn't account for body weight. A more personalized rough guide many sources cite: about 6mg of caffeine per kg of body weight, capped at 400mg.
2026-09-02 Most BMR calculators give you one formula. If you know your body fat %, a second one is more accurate
Mifflin-St Jeor and Katch-McArdle gave nearly identical results for one real body — but they don't always agree, and only one of them accounts for lean mass.
2026-09-01 Picking "Moderate" instead of "Light" activity can throw off your calorie target by 250 a day
The gap between adjacent TDEE activity levels is bigger than most people assume — and most people click the middle option without checking.
2026-09-01 A 0.5 kg/week weight loss goal is exactly a 550 calorie/day deficit — not a guess
The real conversion rate is about 7,700 calories per kilogram of body fat — this calculator does that math directly instead of asking you to pick a round number.
2026-09-01 The US Navy body fat method can output a physiologically impossible number — most calculators never tell you that
For some body shapes, the standard tape-measurement formula produces a result below what's biologically possible. This calculator flags it instead of showing it with false confidence.
2026-09-01 Lean body mass without a body fat test: the Boer formula estimates it from height and weight alone
An 80 kg, 180 cm man has an estimated 61.4 kg of lean mass — useful for protein targets and for a more accurate BMR formula.
2026-09-01 Four "ideal weight" formulas, one height: a 5.8 kg spread that most calculators hide
Devine, Robinson, Miller, and Hamwi were built decades apart for drug dosing, not health targets — and they don't agree with each other.
2026-09-01 A healthy weight isn't one number — for 180 cm, the BMI-based range spans nearly 21 kg
59.9 to 80.7 kg is the full healthy-BMI range at that height — a range, not a target, and this calculator treats it that way.
2026-09-01 Body surface area, not weight, is what determines chemotherapy dosing — here's the formula hospitals actually use
The Mosteller formula is the clinical standard for a reason: simple enough for a quick bedside calculation, accurate enough to trust.
2026-09-01 One pace calculator, three things it can solve — pace, time, or distance, whichever you don't know
A 10 km run in 50 minutes is exactly a 5:00/km pace — and the same triangle works in reverse to plan a race time or distance.
2026-09-01 100 kg for 5 reps: Epley says a 116.7 kg max, Brzycki says 112.5 — both are estimates, not facts
The two most common 1RM formulas don't agree, and the gap grows with higher rep counts — most calculators only show you one of them.
2026-09-01 Karvonen heart rate zones account for your fitness level. A simple percent-of-max doesn't
Two people with the same max heart rate but very different resting rates get different target zones under Karvonen — and identical zones under a plain percentage.
2026-09-01 30 minutes of brisk walking burns roughly 112 calories for an 80 kg person — the MET math behind it
Calories burned during exercise comes down to one standardized number per activity: MET, the metabolic equivalent of task.
2026-09-01 Carb, protein, and fat calculators are usually three separate pages. They're really one calculation
All three macros come from the same total calorie number — raising one percentage always lowers the others, which is invisible if you calculate them one at a time.
2026-09-01 Due date calculators and conception calculators are the same math, run in opposite directions
A June 1 last period gives a March 8 due date under Naegele's rule — and starting from that same due date and working backward lands on the exact same conception estimate.
2026-09-01 Your fertile window isn't just ovulation day — it starts 5 days earlier, because sperm outlasts the egg
For a 28-day cycle starting August 1, the fertile window runs August 10-15, not just the single ovulation date of August 15.
2026-09-01 Most period calculators predict one date. This one predicts the next six
Seeing six cycles ahead — not just the next one — makes it easier to plan around the pattern instead of recalculating month by month.
2026-09-01 Recommended pregnancy weight gain isn't one number — it depends on your BMI before pregnancy
The IOM guideline range for a normal-BMI person is 11.5 to 16 kg — but it shifts significantly for underweight, overweight, and obese starting categories.
2026-09-01 Kidney function calculators changed their formula in 2021 — most online tools never updated
The CKD-EPI equation used to include a race coefficient. The current clinical standard, adopted by the National Kidney Foundation, doesn't.
2026-09-01 "Body type" quizzes ask you to guess. This calculator measures your wrist instead
Ectomorph, mesomorph, endomorph — none of those categories come from a validated formula. Height-to-wrist ratio is an actual measurement.
2026-09-01 A BAC calculator can estimate 0.047% after 3 drinks — but that number should never decide whether you drive
The Widmark formula is a real, widely-cited estimate. It's also missing everything that actually varies between two real people.
2026-09-01 We checked what people actually hate about BMI calculators. Here's what we fixed.
App store reviews, Reddit threads, and WHO guidelines pointed to three specific problems with free BMI calculators. Our BMI Calculator addresses all three directly.
2026-08-28