A doctor and a dietitian checked 35 of our calculators

Our blood alcohol calculator used the textbook Widmark formula, but it left out a factor of 1.055 for the density of blood. Dr. Ilija Kelepurovski, a urologist who reviewed our health calculators, asked us to add it, so every result is now about 5.5% higher. Dr. Kelepurovski also asked for a plainer warning that the time until you are sober can be hours longer than the estimate, and for the signs of alcohol poisoning to appear once the result reaches 0.20%.

That was one of dozens of changes from two expert reviews this month. Here is why we asked for them, what changed, and where you will see the reviewers’ names.

Why we asked for reviews

Every calculator on this site shows its formula, and every worked example is recalculated and checked each time the site is built. That catches arithmetic mistakes. It does not catch a page that follows an outdated guideline, applies adult categories to a child, or shows an alarming number without saying when to call a doctor. For calculators where a wrong number can matter, you need someone who works with those numbers for a living.

So we hired independent experts, paid them for their time, and gave each of them a sheet listing every page in their field. They tried each calculator with realistic and extreme inputs, checked the formula, the limits and the wording against published sources, and told us what to change and why. We made the changes, they checked them again, and their names go on the pages they approved. The reviewers page explains the process step by step.

20 health calculators, reviewed by a urologist

Dr. Ilija Kelepurovski, MD is head of the urology department at Clinical Hospital Bitola in North Macedonia. Dr. Kelepurovski reviewed 20 calculators for body measures, heart health, and pregnancy and the menstrual cycle, approved every one of them with changes, and signed them all off on October 27 after checking our fixes on the live pages. A few of the changes:

• The BMI calculator now says its categories are for adults aged 20 and over, and mentions the lower cut-offs often used for people of Asian descent (23 and 27.5).
• The blood pressure calculator follows the 2025 AHA/ACC guideline. A reading above 180/120 now lists the symptoms that mean you should get emergency care rather than wait and measure again.
• The heart rate zone calculator no longer works out training zones from a resting heart rate above 100. It shows a warning instead.
• The due date calculator stopped showing negative days once the date has passed. It now says how many days past the due date you are, and when a pregnancy counts as late term or post-term.
• The water intake calculator makes clear that its figure is for drinks, that food supplies roughly a fifth of your water, and that anyone told to restrict fluids should follow their doctor, not the calculator.

Most pages also gained a section on when to see a doctor and a list of the sources behind the numbers. The other 15 calculators in this review are ideal weight, body fat, lean body mass, waist-to-hip ratio, waist-to-height ratio, body surface area, max heart rate, sleep, blood alcohol, pregnancy, conception, ovulation, period, pregnancy weight gain and the child height predictor.

15 nutrition and fitness calculators, reviewed by a dietitian

Liz Cook, MS, RD is a registered dietitian in the United States who provides one-on-one nutrition counseling and was previously the sports dietitian at Grand Canyon University. Liz reviewed 15 calculators and approved nine of them as they were: calorie deficit, macro, weight loss, weight loss percentage, pace, marathon pace, the race time predictor, one rep max and steps to miles.

The other six changed:

• The protein calculator used to offer four situations, starting with the 0.8 g/kg recommended dietary allowance for a sedentary adult. It now follows the 2025-2030 Dietary Guidelines for Americans: 1.2 to 1.6 grams per kilogram of body weight a day for healthy adults, and 1.6 to 2.0 for people building muscle or training as athletes. Not every nutrition scientist agrees with the new target, and the page says so and cites both sides.
• The calories burned calculator now uses the 2024 Adult Compendium of Physical Activities instead of the 2011 edition. Some values moved a long way. Gardening dropped from 3.8 to 2.0 MET, and a 160 lb person running at 6 mph for half an hour now burns about 337 calories rather than 356. Weight training is now labeled resistance training, and aerobic dance is split into moderate and vigorous.
• The calorie calculator lists the “gain about half a pound a week” line in its formula. The results always showed it, but the formula skipped it.
• The BMR, TDEE and VO2 max calculators have clearer FAQ answers. The TDEE page, for example, no longer promises that eating below your TDEE will make you lose weight. It says it may.

Liz is re-checking the changed pages now.

Where you will see their names

On each reviewed calculator, a line under the title says who checked it and on what date, and links to the reviewer’s profile. The profile lists their training and credentials and every page they reviewed. For now the credit appears on the English pages, because those are the pages the reviewers read.

Reviewers are paid for their time and have no say in our advertising. If a reviewed page later changes in a way that matters, it goes back to the reviewer, or their name comes off.

Next: money and math

A certified public accountant is working through our loan, mortgage, tax and retirement calculators now. We are still looking for a math teacher or statistician for the math and statistics pages. If that sounds like you, the reviewers page explains how to get in touch.

And if a number on any page looks wrong to you, the feedback link at the bottom of every page comes straight to us.