About FitCalcs

FitCalcs is an independent website that provides free fitness and nutrition calculators. The goal is simple: give you clear, accurate answers to everyday training and diet questions — how many calories you need, how much protein to eat, how fast you ran, how much you could lift — without accounts, paywalls, or clutter. Every tool works instantly in your browser and is free to use.

Who we are

FitCalcs is built and maintained by Jesse, a software developer who reviews fitness and nutrition research as a personal interest. Jesse is not a doctor or registered dietitian — and is careful to say so. The calculators implement well-established, peer-reviewed formulas and present them in a fast, easy-to-use interface. Every result comes with the formula, its source, and an honest description of its limitations, so you can take the numbers to a professional or check the method yourself.

The author page goes further: what Jesse is and is not qualified in, why Jesse is a pen name rather than a legal name, and the specific rules every page on this site is held to.

This is a small, independent project — not a large publisher or medical organization. Because we cannot examine your individual circumstances, we focus on transparency: every calculator shows the exact formula it uses, defines each variable, and cites the original published source.

What is on the site

There are three kinds of page here, because there are three different shapes of question people arrive with.

• 14 calculators — 11 for nutrition and body measurements (calories, macros, protein, body fat, BMI, hydration) and 3 for training and performance (running pace, one-rep max, the energy cost of a workout). Each answers one question for one person.
• 13 reference charts — the same math published as printable lookup tables, for when you want to see the whole range at once rather than a single figure.
• 10 guides — plain-English explainers for the part a number cannot cover: how wide the error bars are, what the formula assumes about you, and what to do when your own data disagrees with it.

How the numbers are calculated

Our calculators use recognized, published formulas rather than numbers we invented. Calorie needs are based on the Mifflin-St Jeor equation combined with standard activity multipliers; body-fat estimates use the U.S. Navy circumference method; strength estimates average several established rep-max formulas. These are estimates to guide you, not exact prescriptions — real results vary from person to person, and you should adjust based on how your body responds.

Each formula is implemented once, in a shared library, and every page that needs it calls the same code. The reference tables are generated when the site is built rather than typed in by hand, so a chart and the calculator behind it cannot drift apart or quietly disagree.

For the full detail on where each formula comes from, how we handle its limitations, and when we last reviewed it, see our methodology and editorial standards.

What this site deliberately does not do

Some of what a site chooses not to do says more than a feature list.

• No accounts and no saved profiles. Nothing to sign up for, and nothing to log into.
• Your inputs stay in your browser. The numbers you type into a calculator are used to compute the result on your own device and are not sent to or stored on our servers. Our privacy policy sets out exactly what is and is not collected.
• No supplements, products, or affiliate links. Nothing here is trying to sell you a protein powder, a meal plan, or a coaching package. There is nothing to buy at all.
• No paywall, ever. No tool is reserved for a paid tier, and none will be.
• No before-and-after marketing and no scare copy. No transformation photos, and no attempt to make you anxious about a number in order to keep you reading.

How the site is paid for

By display advertising — that is the whole model. Keeping the site free for everyone matters more than squeezing revenue out of a small number of subscribers, and hosting a set of static pages is cheap. Advertising is not currently running on the site; when it is, the ad units will be clearly separated from the content, and our privacy policy already describes what advertising partners may use.

Advertisers have no say in what is published. No advertiser sees a page before it goes live, and no formula, recommended range, or piece of wording has been chosen to suit one — the editorial policy commits to that in writing.

Who this is for

The tools are built for healthy adults who want a defensible starting number: someone setting a calorie target for the first time, a runner converting a goal time into a pace, a lifter working out training percentages from a recent set. Where a calculator needs your age, it accepts 18 to 100 and says so, because the formulas behind it were developed and validated in adults — applying them to children is a different question with different equations.

It is not built for clinical use, and it cannot account for pregnancy, a medical condition, a medication that changes appetite or fluid balance, or a history of disordered eating. If any of those apply, the numbers here are at best a conversation starter for someone qualified to examine you.

Not medical advice

FitCalcs is for general educational use by healthy adults. It is not a substitute for professional medical or dietary advice. If you have a medical condition, a history of disordered eating, or are pregnant, please consult a qualified professional before making changes to your diet or exercise.

Corrections and contact

We take accuracy seriously. If you spot a formula that looks wrong, a result that does not add up, or a source that needs updating, please tell us and we will investigate and correct it. Email hello@fitcalcs.app or use the contact page.