About Over40Macros

A calorie and macro calculator built specifically for the people most calculators ignore — adults over 40.

Why we built this

Walk into any gym, open any fitness app, or run any online calculator and you'll find the same thing: tools built around the assumptions of a 25-year-old's body. The standard formulas use the same protein targets, the same activity multipliers, and the same macro ratios for everyone.

That's a problem, because the body you have at 45 is not the body you had at 25. Hormones shift. Muscle becomes harder to build and easier to lose. The way your body processes lipids, alcohol, and even caffeine changes around age 44 — and changes again around 60.

Over40Macros exists to fix that gap. Every calculation, recommendation, and explanation on this site is grounded in current peer-reviewed research on how human metabolism, body composition, and protein needs change after 40.

What makes this calculator different

• Higher protein targets. We default to 1.6g per kg of body weight — within the evidence-based range research recommends for adults over 40 — instead of the outdated 0.8g/kg standard.
• Realistic deficits. Aggressive crash dieting accelerates muscle loss, which is the opposite of what you want after 40. We use a moderate 20% deficit for fat loss and 10% surplus for muscle gain.
• Honest about activity. Most calculators encourage you to overestimate your activity level. Our descriptions are deliberately conservative.
• Science-backed explanations. Every claim we make on this site is linked to a peer-reviewed source so you can verify it yourself.

The science we rely on

The calculations and recommendations on this site are based on:

• The Mifflin-St Jeor equation, the most accurate validated formula for estimating basal metabolic rate in modern adults
• Research on sarcopenia (age-related muscle loss) from PubMed Central, the Cleveland Clinic, and Harvard Health
• The 2024 Stanford Medicine study published in Nature Aging on the biological shifts that occur in our 40s and 60s
• Peer-reviewed studies in Frontiers in Nutrition and Science on protein requirements and energy expenditure across the lifespan

Full citations are linked at the bottom of the calculator page.

Important honest disclosures

This site is supported by advertising (Google AdSense) so the calculator can stay free for everyone. We do not collect, store, or sell any of the data you enter into the calculator — all calculations happen in your browser and disappear the moment you close the tab.

We are not doctors, dietitians, or medical professionals. The information on this site is general in nature and is not a substitute for personalised medical advice. If you have any health condition — including diabetes, heart disease, kidney issues, or eating disorder history — please consult a qualified healthcare provider before changing your diet.

Get in touch

Questions, feedback, or a research paper you think we should cite? Reach us via the contact page.