Most adults need somewhere between 1,600 and 3,000 calories per day and 1.2 to 1.6 grams of protein per kilogram of body weight. But those ranges are wide because the right number for you depends on your size, age, activity level, and goals. Here’s how to get closer to your actual number.
How to Estimate Your Daily Calories
Your body burns a baseline number of calories just to keep you alive: breathing, circulating blood, regulating temperature. This is your basal metabolic rate, or BMR. The most widely used formula for estimating it is the Mifflin-St Jeor equation, which uses your weight, height, age, and sex:
- For men: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
- For women: (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
To convert pounds to kilograms, divide by 2.2. To convert inches to centimeters, multiply by 2.54. A 35-year-old woman who weighs 150 pounds (68 kg) and stands 5’5″ (165 cm) would get a BMR of roughly 1,371 calories. A 35-year-old man at 180 pounds (82 kg) and 5’10” (178 cm) would land around 1,757.
But you don’t lie still all day. To get your total daily calorie needs, multiply your BMR by an activity factor:
- Sedentary (desk job, little exercise): BMR × 1.2
- Lightly active (exercise 1–3 days per week): BMR × 1.375
- Moderately active (exercise 3–5 days per week): BMR × 1.55
- Very active (hard exercise 6–7 days per week): BMR × 1.725
Using the woman from the example above, if she exercises three times a week her estimated daily need is about 1,885 calories. The man at the same activity level would need roughly 2,416. These numbers are estimates, not exact prescriptions. Your actual metabolism can vary by a few hundred calories based on genetics, muscle mass, and other factors. But they give you a solid starting point.
Adjusting Calories for Your Goal
If your goal is to maintain your current weight, eating around your estimated total is the target. If you want to lose weight, a deficit of 300 to 500 calories per day is enough to lose roughly one pound per week, which is considered a healthy, sustainable pace. Cutting more aggressively often backfires: you lose muscle along with fat, energy tanks, and the diet becomes harder to stick with.
If you’re trying to gain muscle, a modest surplus of 200 to 300 calories above your maintenance level gives your body the extra energy it needs to build tissue without adding excessive fat. The surplus matters less than consistent strength training and adequate protein, which is where the next part comes in.
How Much Protein You Actually Need
The old standard recommendation is 0.8 grams of protein per kilogram of body weight per day. For a 150-pound person, that works out to about 55 grams. But that number represents the minimum to prevent deficiency, not the amount for optimal health. The 2025–2030 Dietary Guidelines for Americans updated the recommendation to 1.2 to 1.6 grams per kilogram per day, which for that same 150-pound person translates to 82 to 108 grams daily.
Where you land in that range depends on how active you are. Someone who walks a few times a week and isn’t focused on building muscle can aim for the lower end. If you strength train regularly or are trying to add muscle, the higher end (or even slightly above) makes more sense. Research on muscle building suggests an intake of 1.6 to 2.2 grams per kilogram per day optimizes the body’s ability to repair and grow muscle tissue. For a 180-pound person, that’s 131 to 180 grams daily.
As a percentage of total calories, protein generally falls between 10% and 35% of your daily intake. Most people aiming for general fitness and health do well in the 20% to 30% range.
Protein Needs Change as You Age
After about age 50, your body becomes less efficient at using protein to maintain muscle. This gradual loss of muscle mass, called sarcopenia, accelerates with each decade and contributes to falls, frailty, and loss of independence. To counter it, researchers recommend that adults over 65 consume at least 1.0 to 1.2 grams of protein per kilogram of body weight daily, which is meaningfully higher than the old 0.8-gram minimum many older adults still follow.
For a 160-pound older adult, that means aiming for 73 to 87 grams of protein per day at a minimum. Combining this intake with some form of resistance exercise, even bodyweight exercises or resistance bands, is the most effective strategy for preserving muscle and strength.
How to Spread Protein Through the Day
Your body can only use so much protein at once for muscle repair. Research suggests that 20 to 25 grams of protein per meal is the threshold that maximizes your body’s muscle-building response, and eating protein across four meals spaced roughly three hours apart appears to be more effective than loading it all into one or two sittings. That works out to about 0.4 to 0.55 grams per kilogram per meal.
In practical terms, this means a breakfast with Greek yogurt or eggs, a lunch and dinner each containing a palm-sized portion of meat, fish, or legumes, and a protein-rich snack. Many people undereat protein at breakfast and overeat it at dinner. Redistributing your intake more evenly can improve how much of that protein your muscles actually use, without requiring you to eat any more total food.
Can You Eat Too Much Protein?
For healthy people with normal kidney function, moderate increases in protein are safe. But there is a point of diminishing returns. Beyond about 2.2 grams per kilogram, there’s little additional muscle-building benefit, and very high protein intakes can place extra strain on the kidneys over time. Cleveland Clinic nephrologists caution against going to extremes, even if your kidneys are currently healthy. If you have existing kidney disease or a family history of it, higher protein diets warrant a conversation with your doctor before making changes.
Putting the Numbers Together
Here’s a quick example for a moderately active 40-year-old woman who weighs 155 pounds (70 kg) and is 5’6″ (168 cm), aiming to maintain her weight:
- BMR: (10 × 70) + (6.25 × 168) − (5 × 40) − 161 = roughly 1,389 calories
- Total daily calories (moderately active): 1,389 × 1.55 = about 2,153 calories
- Daily protein target: 70 kg × 1.2 to 1.6 = 84 to 112 grams
- Per meal (4 meals): roughly 21 to 28 grams of protein
If she wanted to lose weight, she’d reduce to about 1,650 to 1,850 calories while keeping protein at the same level or slightly higher. Protein is the last thing to cut when reducing calories, because it preserves muscle mass, keeps you fuller longer, and has a higher thermic effect, meaning your body burns more energy digesting it compared to carbs or fat.
Run your own numbers using the formulas above, pick a protein target in the 1.2 to 1.6 gram range (or higher if you’re training hard), and distribute it across your meals. Those two steps alone put you ahead of most people guessing at their intake.