Macro Calculator
Macro Calculator
Calculate your daily calorie and macronutrient targets based on your stats and goals.
Percentages must add up to 100%
What Are Macros and How Does a Macro Calculator Actually Help You?
Most nutrition advice tells you to “eat clean” or “cut carbs” without ever explaining the numbers underneath. A macro calculator skips the vagueness and tells you exactly how much protein, carbs and fat your body needs based on your actual stats and goals.
What Macros Are (and Why Calories Alone Don’t Cut It)
Macros is short for macronutrients. There are three of them: protein, carbohydrates and fat.
Carbs are what your body reaches for first when it needs energy. Protein builds and repairs muscle. Fat keeps your hormones in order. Don’t skip it. You need all three. The question is how much of each.
Here’s the thing: two people can eat the same number of calories and get completely different results, depending on where those calories come from. Someone eating 2,000 calories mostly from protein and vegetables will hold onto muscle and feel full. Someone eating 2,000 calories mostly from refined carbs and oils will feel sluggish and lose muscle at the same time as fat. Same calories. Very different outcomes.
That’s why macros matter more than calories alone.
BMR vs TDEE: The Numbers You Actually Need to Know
Before any macro calculator can give you useful numbers, it needs to know how many calories your body burns in a day. That’s where BMR and TDEE come in.
BMR stands for Basal Metabolic Rate. It’s the number of calories your body burns just to keep you alive, breathing, and functioning, even if you lay in bed all day. For most adults, BMR sits somewhere between 1,400 and 2,000 calories depending on age, sex, height and weight.
TDEE stands for Total Daily Energy Expenditure. Then it factors in how much you actually move. A sedentary office worker might have a TDEE of 1,900 calories. The same person doing intense training five days a week could have a TDEE closer to 2,800.
TDEE is the number you build your targets around. Eat at your TDEE and your weight stays roughly the same. Eat below it and you lose weight. Eat above it and you gain.
Worth knowing: TDEE for women tends to be lower than for men at the same height and weight, mostly because men tend to carry more muscle mass, which burns more calories at rest.
Which formula does this calculator use?
This calculator uses the Mifflin-St Jeor equation to estimate your BMR. It’s the most widely validated formula for non-athletes and is consistently more accurate than the older Harris-Benedict equation, which was developed in 1919 and tends to overestimate calorie needs by around 5% for most people.
One limitation worth knowing about: Mifflin-St Jeor uses total body weight, not lean mass. This means it can slightly overestimate TDEE for people with higher body fat and slightly underestimate it for very lean, muscular individuals. If you know your body fat percentage, the Katch-McArdle formula (which uses lean mass) is more precise, though the difference for most people is small.
How a Macro Calculator Works Out Your Numbers
A good macro calculator takes your age, sex, height, weight and activity level to estimate your TDEE, then adjusts the numbers based on your goal: losing fat, building muscle or staying where you are.
Then it splits your calories into macro targets. A common starting split for general fat loss is roughly 40% protein, 35% carbohydrate and 25% fat, though this varies based on body composition, how much training you do, and personal preference.
To put that in real numbers: if your TDEE is 2,200 calories and you’re aiming to lose weight on a 500-calorie deficit, you’d be eating 1,700 calories a day. At a 40/35/25 split, that’s around 170g of protein, 149g of carbs and 47g of fat. Specific targets you can actually track, rather than vague instructions to “watch what you eat.”
A 500-calorie daily deficit, by the way, works out to roughly 0.5kg of weight loss per week. Sustainable, not dramatic. That’s usually the goal.
Macro splits by goal: a quick reference
These are the starting splits most commonly used and supported by the evidence. They’re not fixed rules. Some people do better with more or fewer carbs based on how they train and how they feel. But if you’re not sure where to start, these are solid defaults.
| Goal | Protein | Carbs | Fat | Calorie target |
| Fat loss | 40% | 35% | 25% | 500 kcal deficit |
| Muscle gain | 30% | 40% | 30% | 250–500 kcal surplus |
| Maintenance | 30% | 40% | 30% | At TDEE |
| Body recomposition | 40% | 35% | 25% | At TDEE (slight deficit optional) |
What about body recomposition?
Recomposition means losing fat and building muscle at the same time. It’s slower than either dedicated cutting or bulking, but it’s realistic for three groups: people who are new to training, people returning after a long break, and people who are carrying enough body fat that their body has energy reserves to draw on while building muscle.
For recomposition, eat at or very close to your TDEE, keep protein high (at least 1.8-2.0g per kg of bodyweight), and prioritise resistance training. The scale may barely move for weeks. That’s not a sign it’s not working. Body composition can shift significantly even when weight stays flat.
How Many Calories Do I Burn in a Day? Why the Answer Varies More Than You Think
People often search “how many calories do I burn a day” expecting a clean number. The honest answer is that it depends, and it changes.
Your calorie burn shifts based on your weight (heavier people burn more), your muscle mass (muscle tissue is metabolically active, fat isn’t), your age (metabolism slows slightly with age) and how much you move. Two people who both “work out three times a week” could have wildly different TDEEs if one person walks 12,000 steps a day and the other sits at a desk for ten hours.
A calorie calculator for weight loss gives you a solid starting point. It’s not gospel. The real test is what happens to your weight over two to three weeks. If you’re eating at a supposed deficit and not losing anything, your actual TDEE is probably lower than the calculator suggested. Try it, watch what happens, tweak if needed.
What Most People Get Wrong With Macros
The biggest mistake is treating protein as optional. Most people trying to lose weight undereat protein and then wonder why they feel hungry all the time and why the scales drop but they end up looking softer rather than leaner. Protein keeps you full and it’s what stops your body from eating into muscle when you’re eating less. Skimping on it makes the whole process harder.
The second mistake is obsessing over exact numbers every single day. Your body doesn’t operate on 24-hour windows. Being a little over on carbs one day and a little under the next averages out fine. What matters is the weekly trend, not daily perfection.
And that’s where most people go wrong with macro calculators specifically: they get the numbers, track for a week, see imperfect results, and conclude it “doesn’t work.” Give it three weeks of consistent tracking before you adjust anything. One week isn’t enough data.
Finally, don’t ignore fat. Fat got a terrible reputation in the 90s and a lot of people still drop it too low. Going under about 0.5g of fat per kilogram of bodyweight starts to mess with hormone production. A 70kg person probably shouldn’t go below 35g of fat per day, regardless of what a very aggressive cut might suggest.
What to Do With Your Macro Numbers Day to Day
Getting your numbers from the calculator is step one. Actually using them is where most people need a bit more guidance.
The most practical approach is to track your food in an app, MyFitnessPal and Cronometer are both free and have large food databases. Log what you eat each day and aim to finish close to your targets for protein, carbs and fat. You don’t need to hit them exactly. Being within 10% of your targets on most days will get you results.
A few things that make daily tracking easier:
- Weigh food rather than measuring by volume where you can. A cup of oats varies much more than 80g of oats. Small errors in estimation compound over a week.
- Pre-log the day before if possible. Trying to hit your protein target at 9pm is harder than planning for it from the start.
- On days you can’t weigh or track precisely, use your best estimate and move on. One imprecise day won’t undo a week of consistent tracking.
- Check your weekly average rather than each individual day. Most tracking apps show this. A week where you hit your targets 5 out of 7 days is a good week.
If splitting macros across meals matters to you: there’s no magic number of meals. What does help is spreading protein across three or four sittings (roughly 30-40g per meal) rather than front-loading it all at once, since your body can only use so much for muscle protein synthesis at a time. Carbs around your training sessions tend to improve performance and recovery. Beyond that, eat in the pattern that you can actually sustain.
Using the Calculator Above
The macro calculator at the top of this page takes your numbers and spits out daily targets for protein, carbs and fat. Plug in your stats, pick your goal and use the output as your starting point.
Adjust after two to three weeks based on actual results. The calculator gives you the framework. Your body gives you the feedback.
Frequently Asked Questions
Macros raise a lot of questions, especially when you’re starting out. Here are the ones we hear most often.
How accurate is a macro calculator compared to an actual metabolic test?
FAQA macro calculator using the Mifflin-St Jeor equation is typically within 10% of your real TDEE for most healthy adults. A lab metabolic test is more precise, but also costs hundreds of pounds and isn’t practical for most people. The calculator gives you a solid starting estimate. Use your actual weight trend over two to three weeks to confirm whether the numbers are right for you.
Do I need to hit my macros exactly every day, or is being close enough fine?
Close enough is fine. Your body doesn’t run on 24-hour accounting. Being 15g over on carbs one day and 15g under the next has no meaningful effect on your results. What matters is your weekly average. Aim to hit your targets most days, accept that some days you won’t, and don’t let one bad day turn into a bad week.
Why am I not losing weight even though I’m eating at a deficit?
A few likely reasons. First, the calculator’s activity multiplier may be too high, so your actual TDEE is lower than the estimate. Second, tracking errors add up fast. Research consistently shows people underestimate their food intake by 20-30%, even when they think they’re being careful. Weighing food rather than measuring by eye tends to close that gap quickly.
How accurate is a macro calculator compared to an actual metabolic test?
FAQA macro calculator using the Mifflin-St Jeor equation is typically within 10% of your real TDEE for most healthy adults. A lab metabolic test is more precise, but also costs hundreds of pounds and isn’t practical for most people. The calculator gives you a solid starting estimate. Use your actual weight trend over two to three weeks to confirm whether the numbers are right for you.
Should I recalculate my macros as I lose weight?
Yes. Your TDEE drops as your body weight drops, because a smaller body burns fewer calories at rest. A rough rule of thumb: recalculate every time your weight changes by around 5kg, or every 8 to 10 weeks. If you don’t adjust, you’ll gradually eat less of a deficit and your progress will stall even though nothing else has changed.
I work out a lot but I’m not losing weight. Should I eat more or less?
Probably neither, at least not yet. The most common culprit is overestimating calorie burn from exercise. An hour of moderate cardio burns around 300-400 calories, not the 700 that most gym machines display. If you’re logging exercise as “extra calories earned” and then eating them back, you may be sitting close to maintenance without realising it. Check your activity level setting in the calculator and make sure it already accounts for your training.
Are macro calculators less reliable for women over 40?
Somewhat. The standard formulas were built on population averages that don’t fully account for the metabolic changes that come with perimenopause or menopause. Lower estrogen affects how the body distributes fat and processes carbohydrates. The calculator still gives you a reasonable starting point, but women in this phase often find they need to trim the calorie estimate by 100-150 calories to see results, and that keeping protein high (around 1.8-2.0g per kg of bodyweight) makes a bigger difference than adjusting carbs or fat.
Does it matter what time of day I eat my macros?
00For most people, not much. Total daily intake drives the vast majority of fat loss or muscle gain results. That said, getting protein spread across three to four meals (roughly 30-40g per sitting) does help with muscle protein synthesis if building muscle is your goal. And eating most of your carbs around training can improve performance and recovery. But if hitting your daily targets consistently is already a challenge, meal timing is the last thing to worry about.
Can I use a macro calculator on a low-carb or keto diet?
Yes. A macro calculator works for any eating style. For a ketogenic approach, you’d typically set fat to around 70-75% of calories, protein to 20-25% and carbs to 5-10% (usually under 50g per day). The calculator establishes your calorie target first, then you allocate those calories across macros in whatever ratio fits your approach. The calorie maths stays the same regardless of which macro you prioritise.
My macro numbers seem really high in protein. Is that normal?
Probably, yes. Most people are used to eating far less protein than the research supports for fat loss and muscle retention. A target of 1.6-2.2g of protein per kilogram of bodyweight can look alarming if you’ve never tracked before, but it’s backed by a large body of evidence. To put it in food terms: hitting 150g of protein a day might mean 200g of chicken breast, a pot of Greek yogurt, two eggs and a protein shake. Spread across three meals, it’s very doable.
Disclaimer: This calculator is intended for informational purposes only and is not a substitute for professional medical or nutritional advice. Figures are estimates based on population-level formulas and individual results will vary. If you have a health condition, are pregnant or breastfeeding, or have a history of disordered eating, please consult a registered dietitian or GP before making changes to your diet.