Guesswork is where most nutrition plans fall apart. These free health calculators give you a starting number for the things people most often get wrong, and each one explains the formula behind it rather than just producing a figure.
Everything runs in your browser. Nothing gets stored, nothing gets sent anywhere and none of them ask for an email address.
All four are free, need no sign up and store nothing. Everything runs in your browser. They give general estimates and do not replace advice from your doctor or a registered dietitian.
What Each One Does
Keto Macro Calculator. Works out your daily fat, protein and net carb targets using the Mifflin-St Jeor equation, then breaks them down per meal. It sets protein by bodyweight rather than as a fixed percentage, which protects muscle better than the usual approach.
Protein Intake Calculator. Gives a daily range using current guidance rather than the 1943 RDA that most calculators still run on. It shows the old figure alongside your range so you can see the difference, and translates your target into eggs, chicken, yogurt and lentils.
Water Intake Calculator. Accounts for your weight, exercise, the weather and pregnancy or breastfeeding. It also shows how much of your total arrives through food, which means the amount you actually have to drink is smaller than the headline number.
Fiber Intake Calculator. Shows your target, the gap from what you eat now, and which single foods would close it. Fiber is the nutrient the largest share of adults fall short on, and most people have no idea by how much.
The Rest of the Set
Eight more calculators cover the numbers that are easiest to get wrong.
- Caffeine calculator: how much is still in you at bedtime, based on a half life of about five hours
- Sleep calculator: bedtime windows that fit whole sleep cycles rather than a flat 8 hours
- Heart rate zone calculator: better zones than 220 minus age
- Sodium intake calculator: where your salt actually comes from, which is mostly packaged food
- Added sugar calculator: a day of food converted into teaspoons
- Net carb calculator: how to read a label properly
- Daily calorie calculator: TDEE, BMR, macros and BMI in one place
- Attention fragmentation tracker: why screen time is the wrong number to watch
How to Read the Numbers
Every calculator here produces an estimate rather than a rule.
Individual variation is real. Two people with identical height, weight and age can differ by 10 to 20 percent in energy needs. Muscle mass, genetics and how much you move without noticing all play a part.
Use the number as a starting point. Try it for two or three weeks, watch what happens, then adjust. Results beat formulas.
Ranges are more honest than single figures. The protein and fiber calculators show ranges deliberately, because that is what the research supports.
Recalculate when things change. Every 10 pounds of weight change, or whenever your activity shifts substantially.
Where the Reference Values Come From
Every calculator here is built on published figures rather than invented ones: the 2025 to 2030 Dietary Guidelines for Americans for protein, fibre, sodium and added sugar, and the National Academies intake levels for water. Nutrition figures throughout come from USDA FoodData Central, and you can check any ingredient yourself there.
Who Should Not Use These
Some conditions require the opposite of what a general calculator suggests.
Chronic kidney disease. Protein usually needs limiting rather than increasing, and fluid may need restricting too.
Heart failure. Fluid restriction is common.
Liver disease. Protein and fluid may both need adjustment.
IBS, Crohn’s disease, ulcerative colitis or a recent diverticulitis flare. Fiber sometimes needs limiting rather than increasing.
Type 1 diabetes, or type 2 managed with insulin. Large dietary changes usually require medication adjustments.
Pregnancy. Needs shift and your provider should guide them.
Any history of disordered eating. Tracking numbers can make things worse rather than better.
Follow your doctor or a registered dietitian rather than any calculator in these situations.
What We Use Them For
Each calculator connects to articles on this site.
The macro calculator pairs with our keto cheesecake, crispy keto waffles and fudgy keto brownies, all of which list net carbs per serving.
The protein calculator pairs with our high protein smoothie recipes and 30 filling breakfast recipes.
The water calculator pairs with our most hydrating foods ranked by water content and 10 infused water recipes.
Frequently Asked Questions
Are these calculators free?
Yes. No sign up, no email required and no limits on use.
Do you store my information?
No. Everything runs in your browser and nothing gets sent to a server or saved anywhere.
How accurate are they?
They give reasonable estimates from established equations. Real needs vary between people with identical measurements, so treat any result as a starting point rather than a precise figure.
Which formulas do you use?
The macro calculator uses Mifflin-St Jeor for energy needs. The protein calculator uses grams per kilogram of bodyweight based on current dietary guidance. The fiber calculator uses Institute of Medicine values. Each page explains its own method.
Can I use these on my phone?
Yes. All of them work on mobile.
How often should I recalculate?
Every 10 pounds of weight change, or whenever your activity level shifts noticeably.
Final Thoughts on These Health Calculators
Numbers help most when you treat them as a starting point. These health calculators give you somewhere sensible to begin rather than a target to obey, and each page explains the reasoning so you can judge whether it fits your situation.
Try a number for two or three weeks, watch what actually happens and adjust from there. Talk to your doctor before making large changes, particularly with kidney disease, diabetes, heart failure or during pregnancy.
These calculators provide general estimates for healthy adults and do not replace advice from your doctor or a registered dietitian. Read our full medical disclaimer and fact checking policy.