Want to know how much fat you have to lose — or how much lean mass you carry?
You’re in the right place. This calculator will help you estimate both.

⚠️ AssumptionS (And Why At Least One Will Not Hold For You)

1. Lean body mass is assumed to stay constant during weight loss.

This means all of the energy burned to fuel your calorie deficit comes from fat tissue, not muscle mass. That’s likely to hold true if you:

• Train hard and consistently (see our free training programs),
• Lose weight at an appropriate pace (~0.5–0.75% of body weight per week), and
• Eat enough protein.

That said, while optimal muscle growth doesn’t happen in a calorie deficit, you can still gain some muscle — especially if you’re relatively new to training, losing weight slowly, or coming from a suboptimal diet. Just don’t expect those gains to offset fat loss in a noticeable way.

2. No other weight loss is accounted for, which isn’t realistic.

If you have ever dieted before, you probably saw a rapid drop on the scale. But this initial “whoosh” was mostly water, gut content, and glycogen — not fat.

So, if you lose 8 pounds in the first two weeks (not uncommon with larger clients) but then 1 pound every week after, your fat loss in those first two weeks is 2 pounds, and your water, gut content, and glycogen losses are 6 pounds.

Most people confuse this initial whoosh with some astonishing success with their new diet. This provides a valuable initial boost to their motivation, but this misunderstanding can have consequences.

To reach your target body fat percentage, you’ll need to temporarily lose more weight than the calculator shows*.

This can range from 3 to 8 pounds, depending on your body size and the magnitude of the diet changes you made.

And know that you’ll regain a large part of the initial whoosh weight (water, glycogen, and gut content) once you return to maintenance calories. Here’s how that looks:

You’ll note that this is the same kind of thing that happens after a couple of days of overeating.

*There’s one exception to this “you will need to lose more weight than you calculate” rule, and it’s people who switch from a very low-carb (keto-style) diet to a moderately carby diet. Your weight may not change in this case, or it may even increase slightly (despite being on lower calories). This occurs due to the increase in water, gut content, and glycogen.

Don’t Make The Mistake of Stopping Your Diet Too Early

Many people reach their target body weight and then panic that they don’t look as lean (defined) as they had thought they would. They start to feel skinny.

This is natural.

1. People underestimate their body fat percentage.
2. They don’t realize that about the water, gut content, and glycogen rebound.
3. And they are the leanest they will ever be before the definition comes through when they start to look bigger at a lighter weight.

Unfortunately, people often abandon their cut too early because they feel they need to bulk. This is where the common slide into the black hole of “physique purgatory” begins. — Don’t make this mistake.

The Fat Loss Calculator’s Equations

Lean Body Mass = Current Weight × (1 - Current Body Fat Percentage ÷ 100)

Example: If someone weighs 180 lbs with 20% body fat:

• Lean Body Mass = 180 × (1 – 0.2) = 180 × 0.8 = 144 lbs

Target Weight = Lean Body Mass ÷ (1 - Target Body Fat Percentage ÷ 100)

Example: Using the same person who wants to reach 15% body fat:

• Target Weight = 144 ÷ (1 – 0.15) = 144 ÷ 0.85 = 169.4 lbs

Weight to Lose = Current Weight - Target Weight

Example: Continuing with our example:

• Weight to Lose = 180 – 169.4 = 10.6 lbs

Next Steps

Now that you have calculated how much weight you have to lose to get to your target.

1. Use our Calorie and Macro Calculator.
2. Enter your email address in the box below to get our free Transformation Kickstart Bundle.