Guides and explainers
Plain-English breakdowns of the numbers behind the calculators, with sources you can check.
Are AI meal plans accurate? Calories, macros and reality
AI can build a meal plan in seconds, but is the math right? Here is where the errors actually come from, how big they are, and how to check a plan yourself.
ReadAre AI Workout Plans Good? What They Get Right and Wrong
AI can build a technically sound training plan in seconds. Whether that plan is good for you depends on four things AI handles very unevenly.
ReadAverage BMR by age and gender
Basal metabolic rate depends on size, sex and age. Here is a chart for typical men and women from 20 to 70, and what the numbers can and cannot tell you.
ReadBench press standards by bodyweight
How much should you bench for your size? Here are bodyweight-ratio standards for men and women, how to test safely and how to use them.
ReadBMI vs Body Fat Percentage: When Each One Misleads You
BMI is quick but blind to muscle, while body fat percentage is richer but harder to measure. Here is how each one works and when to trust it.
ReadBMR vs TDEE: What Each Number Means and How They Relate
BMR is the energy you burn at complete rest, while TDEE is your full daily burn including movement and digestion. Here is how they fit together.
ReadHow to Set a Calorie Deficit to Lose Weight
Fat loss rests on one simple idea: spend more than you eat. Here is how to set your deficit without starving.
ReadWhat Is a Calorie Surplus? The Right Size for Lean Bulking
Eating more than you burn is necessary to build muscle, but the size of the surplus matters. Here's how to find the sweet spot for lean gains.
ReadHow many calories do 15,000 steps burn?
15,000 steps is a serious walking day of more than 10 km. Here is what it burns at your weight and pace, and how to fit it into a week.
ReadHow many calories do 5,000 steps burn?
5,000 steps is about 3.5 km of walking. Here is what that burns at your weight and pace, and what the number does and does not mean.
ReadCalories Burned Running Per Mile: What the Research Actually Says
Running is one of the highest calorie-burning exercises available — but the exact number per mile varies more than most people realize.
ReadCalories Burned Walking: How to Estimate Any Walk
Walking burns calories in proportion to your body weight, your pace and how long you keep moving. Here is how to estimate it without guessing.
ReadHow many calories does walking burn per kilometre?
A simple rule covers most walkers: about 0.7 to 0.8 kcal per kilogram of body weight for every kilometre. Here is the table, and where the rule breaks.
ReadCalories In vs Calories Out: Energy Balance Explained
Energy balance is the simple rule behind weight change: calories in versus calories out. Here is what it really means and where it gets nuanced.
ReadDaily calorie needs for men by age
Calorie needs for men drop a little each decade, but body size and activity matter much more. Here is the table and how to make it yours.
ReadDaily calorie needs for women by age
Calorie needs for women fall slowly with age but depend far more on body size and activity. Here is a table you can read in seconds, and how to personalise it.
ReadDoes Protein Timing Matter? The Anabolic Window, Honestly
The short answer: total daily protein matters most, the post-workout window is wide, and even meal distribution offers modest gains. Here is the honest breakdown.
ReadIs BMI Accurate? What It Gets Right and Wrong
BMI is everywhere, but it has clear limits. Here is what it is good for and when you need other numbers.
ReadHow long does it take to lose 10 kg?
10 kg of fat is roughly 77,000 kcal. Here is how long that takes at different daily deficits, and why real progress is a little slower than the maths.
ReadHow Many Calories Do I Burn a Day? Calculate Your TDEE
Your daily calorie burn is more than just your workouts. Learn how to estimate your total daily energy expenditure with science-backed formulas.
ReadHow Many Calories Do 10,000 Steps Burn?
10,000 steps has become a global daily step goal, but how many calories does it actually burn? The answer depends on your body and how you walk.
ReadHow Many Calories to Build Muscle (Surplus Guide)
Muscle needs a small calorie surplus on top of maintenance. Here is how big to make it and how to grow with minimal fat gain.
ReadHow Many Calories Should You Eat on Rest Days?
Rest days do not switch off your metabolism. Here is a practical, evidence-based way to set rest-day calories without overthinking any single day.
ReadHow Many Calories to Burn to Lose 1 kg of Fat?
One kilogram of body fat stores about 7,700 kcal of energy. Here is how that translates into a daily deficit, a realistic weekly rate, and why the scale never quite matches the arithmetic.
ReadHow Many Calories to Maintain Your Weight
Maintenance calories are the amount that keeps your weight steady. Here is how to estimate the number and confirm it in real life.
ReadHow Many Steps to Lose a Pound of Fat?
Walking is one of the most sustainable fat-loss tools available. Here's the real math on how many steps it takes to drop a pound — and how to use it strategically.
ReadHow much protein per day do women need?
The minimum and the optimal protein intake for women are not the same number. Here is a table by bodyweight and goal, and how to hit it with real meals.
ReadHow Much Protein Per Day to Lose Weight
Protein is the most important macro when you are losing weight. Here is a practical daily target that protects muscle and curbs hunger.
ReadHow much protein do you need to build muscle
Protein targets get argued to death online. The research is actually pretty settled. Here is the range that builds muscle and how to reach it.
ReadHow Much Water Should You Drink a Day
There is no single magic number for water. Your needs shift with heat, exercise, and body size. Here is how to find a target that fits you.
ReadHow to Build Your Own Workout Routine (Step by Step)
You do not need a template someone else wrote. Here is the full process for building a workout plan that fits your schedule, your goal and your recovery.
ReadHow to Calculate Lean Body Mass (Boer Formula)
Lean body mass is everything in your body that is not fat. Here is how to estimate it with the Boer formula and why the number is worth tracking.
ReadHow to Calculate Your Macros for Cutting
Cutting is not just eating less. It is eating in a deficit while keeping protein high enough to protect muscle. Here is how to set your macros.
ReadMaximum Heart Rate Formula: Calculate It by Age
Max heart rate helps you set training zones. Here are the common formulas, their limits, and how to turn the number into zones.
ReadHow to calculate your TDEE (and actually use it)
Your TDEE is the number every diet math starts from. Here is how to work it out and turn it into a calorie target you can hit.
ReadHow to Estimate Your One Rep Max
You can estimate a one rep max from a set you already did. Here are the Epley and Brzycki formulas and how to use them safely.
ReadHow to Reverse Diet Safely After a Cut
After a cut, jumping back to old habits often backfires. A reverse diet raises calories in small steps so you keep results and feel human again.
ReadHow to Set a Daily Step Goal
A step goal only helps if it fits your life. Here is how to set a realistic target and grow it without burning out.
ReadHow to set your macros for your goal
Macros sound technical but the order is simple. Set protein, set fat, let carbs fill the rest. Here is how to do it from your calorie target.
ReadIdeal Body Weight Formula: Hamwi, Devine and More
Ideal body weight formulas give a quick target number from your height, but they were built for a narrow purpose. Here is how they work and where they fall short.
ReadIs 1,200 Calories a Day Too Low?
The 1,200-calorie floor is an old default, not a personalized target. For most adults it undershoots real needs and backfires. Here's how to set a smarter deficit.
ReadMacros for Muscle Gain Explained: How Much Protein, Carbs, and Fat You Need
Building muscle requires more than lifting heavy — your macronutrient split determines whether your body has the raw materials to actually grow.
ReadFitness App in Your Own Language vs a Fitness Tracker
Most fitness apps assume you read English comfortably. If you don't, the friction shows up everywhere: half-understood instructions, mislogged meals, ignored reminders. Here is why language is an adherence variable, not a cosmetic one.
ReadPersonal Trainer Cost Per Month: The Real Math (2026)
Sticker prices run from $0 to $600 a month. The smarter question is what each completed workout costs you, because a plan you skip is the most expensive kind.
ReadProtein Per Kg of Bodyweight: How Much Do You Actually Need?
Protein recommendations are everywhere, but they often conflict. Here's what the research actually says about protein per kg of bodyweight for different goals.
ReadResting Metabolic Rate: What It Is and How to Estimate It
Most of the calories you burn happen while you do nothing. Resting metabolic rate is that baseline, and it drives your daily energy needs.
ReadSteps to Calories, Explained
Turning step counts into calories is possible, but it depends on stride, weight and pace. Here is how the conversion really works.
ReadTDEE for Women Explained: Why Your Calorie Needs Are Different
Women's calorie needs are not simply lower versions of men's needs. Hormones, menstrual cycle phase, and body composition create unique patterns that require specific guidance.
ReadWaist-to-Height Ratio: The Simple 0.5 Rule
Waist to height ratio is one of the simplest health checks you can do at home. Here is how it works, the 0.5 threshold, and why it often beats BMI.
ReadHealthy Body Fat Percentage: Ranges by Sex and Age
Body fat percentage says more than the scale. Here are the healthy ranges and how to measure them without pricey gear.
ReadWhat Is 1RM? How to Calculate Your One-Rep Max
1RM sits at the heart of any strength program. Here is how to estimate it safely and use the percentages in your training.
ReadZone 2 heart rate explained: your bpm range by age
Zone 2 is easy, steady cardio you can hold while talking. Here is the heart-rate range by age, how to personalise it and what it is good for.
ReadFrequently asked questions
The CalcFitLab blog is where the calculators get explained in plain English — what each number means, where the formula comes from, and how to act on the result. Every guide cites its sources and links back to the tool it covers. Here are the questions readers ask most.
What do the CalcFitLab guides cover?
The guides explain the numbers behind the calculators: how TDEE is worked out, why protein targets land where they do, what BMI does and does not tell you, and how to read a one-rep-max estimate. Each one is written to stand on its own and links back to the tool it explains.
Who writes these articles?
The CalcFitLab editorial team, part of the team behind the Trainera platform, publishes them and checks them against the sources they cite. Every health claim is tied to a named source such as the NHS, WHO or ACSM, so you can check it rather than take it on trust.
How often are the guides updated?
Each article carries a published and an updated date. When a guideline changes or a better source appears, we revise the piece and re-date it instead of leaving old numbers in place.
Do I need to read a guide to use a calculator?
No. The calculators work on their own. The guides are there for when you want to understand where a number comes from or how to act on it, not as a step you have to take first.
Are the guides free?
Yes. Everything on CalcFitLab is free and needs no sign-up. There is no paywall and no account — you can read any guide and use any tool as often as you like.
Which guide should I read first?
If you are setting up a plan, start with the TDEE and macro explainers, because those numbers drive everything else. From there the training and body-composition guides add detail.