Last reviewed: October 2026 by the Get Tips For Better Life Editorial Team
Every tool on this site uses a published formula or guideline from a government health agency, a professional organization or peer-reviewed research. This page lists the method behind each one, so you can see exactly where your result comes from.
Our Rules for Every Calculator
- Published methods only. We don’t invent formulas. Each tool names its method and links the source on its own page.
- Tested before publishing. We check every tool with several example inputs (and the examples shown on the page) against the published formula, on mobile and desktop.
- Limits are stated. Each tool says who it may not suit and that it can’t diagnose anything.
- Your data stays with you. The calculators run in your browser. We don’t store or send what you enter.
- Reviewed regularly. We re-check every tool at least once a year and whenever a guideline changes.
The Method Behind Each Tool
Calories and metabolism
| Tool | Method | Main source |
|---|
| BMR Calculator | Mifflin-St Jeor (plus revised Harris-Benedict and Katch-McArdle for comparison) | Mifflin et al., Am J Clin Nutr, 1990 |
| TDEE Calculator | Mifflin-St Jeor BMR × standard activity factors | Mifflin et al., 1990 |
| Calorie Calculator | Mifflin-St Jeor with activity and goal adjustment | Mifflin et al., 1990; NIDDK Body Weight Planner |
| Calorie Deficit Calculator | TDEE minus your chosen deficit, with a 1,200-calorie floor | Mifflin et al., 1990; CDC; NIDDK |
| Menopause Calorie Calculator | Mifflin-St Jeor, protein per meal, nutrient targets by age | Mifflin et al., 1990; PROT-AGE (2013); NIH Office of Dietary Supplements |
| Macro Calculator | Calorie target split into protein, carbs and fat within the Dietary Guidelines ranges | National Academies (DRIs); Dietary Guidelines for Americans |
| Weight Loss Timeline | Projected weekly loss from your calorie deficit | CDC; NIDDK Body Weight Planner |
| Intermittent Fasting Calculator | Eating window from your first meal time and chosen schedule | Johns Hopkins Medicine |
Nutrition
| Tool | Method | Main source |
|---|
| Protein Calculator | Grams per kg of body weight by goal, with adjusted weight for higher BMIs | PROT-AGE Study Group (2013) |
| Fiber Calculator | Adequate Intake by age (25 g / 21 g) and 14 g per 1,000 calories | National Academies; Dietary Guidelines for Americans; Mayo Clinic food chart (USDA data) |
| Water Intake Calculator | Adequate Intake of about 2.7 L total water a day for women, adjusted for activity and climate | National Academies |
Body size and composition
| Tool | Method | Main source |
|---|
| BMI Calculator and BMI Over 50 | Weight (kg) ÷ height (m)², CDC categories; older-adult range noted | CDC; Winter et al., Am J Clin Nutr, 2014 |
| Height and Weight Chart | Weights matching BMI 18.5 to 24.9 for each height | NHLBI |
| Ideal Weight Calculator | Devine, Robinson, Miller and Hamwi formulas compared | Published formulas (1964 to 1983) |
| Body Fat Calculator | U.S. Navy tape-measure method | Hodgdon and Beckett, Naval Health Research Center |
| Body Fat Percentage Chart | Healthy ranges by age; fitness categories | Gallagher et al., Am J Clin Nutr, 2000; American Council on Exercise |
| Lean Body Mass Calculator | Boer, James and Hume formulas | Published formulas |
| Waist-to-Hip Ratio Calculator | Waist ÷ hips; WHO cut-off 0.85 for women; waist 35 in; waist-to-height 0.5 | WHO (2008); NHLBI |
| Body Shape Calculator | Bust, waist and hip proportions | WHO (2008) waist guidance; NHLBI |
| Body Frame Size Calculator | Wrist size by height; elbow breadth; Hamwi weight by frame | MedlinePlus; Metropolitan Life tables (1983) |
Activity and heart rate
Health tracking
What Our Calculators Can’t Do
- They give estimates, not diagnoses. Real bodies vary.
- They’re designed for healthy adults. They may not suit you if you’re pregnant, under 18, an elite athlete, or have a medical condition that affects weight, metabolism or heart rate.
- They don’t replace advice from your doctor, a registered dietitian or another health professional.
Found a Problem?
If a result looks wrong, please email contact@gettipsforbetterlife.com with the page link and the numbers you entered. We aim to reply within 3 business days and correct confirmed errors quickly.
Read our Editorial Policy and Medical Disclaimer.
