Health & Fitness
Lean Body Mass Trend Calculator
Project weekly body weight, fat percentage, lean mass, and fat mass using separate linear change assumptions.
Starting estimated lean mass (kg)-
Projected ending weight (kg)-
Projected ending body-fat percentage-
Projected ending lean mass (kg)-
Projected lean-mass change (kg)-
Projected fat-mass change (kg)-
Decision view
Lean-and-fat stacked area trend
Lean-and-fat stacked area trendEvery projected week partitions body weight into lean and fat mass.
Exact scenario comparisonPlanned weekly weight change (kg) changes while all other entered assumptions remain constant.
| Planned weekly weight change (kg) | Starting estimated lean mass (kg) | Projected ending weight (kg) | Projected ending body-fat percentage | Projected ending lean mass (kg) | Projected lean-mass change (kg) | Projected fat-mass change (kg) |
|---|
Period-by-period detail
Weekly body-composition projection table
How to use Lean Body Mass Trend Calculator
- Enter starting measurements and separate weekly changes.
- Choose the projection horizon.
- Inspect the stacked area trend and weekly table.
Calculator guide
Understanding Lean Body Mass Trend Calculator
Weight and body-fat percentage can change at different rates, so lean and fat mass must be recalculated together at every week.
Calculation method
How the calculation works
Apply separately entered weekly weight and body-fat percentage-point changes, then recalculate lean and fat mass at every displayed week. Advance weight and body-fat percentage by their entered weekly changes, then calculate lean and fat components from each weekly pair.
Detailed calculation process
Recalculate body composition across a linear weekly trend
The default starts at 82 kg and 24%, changes weight by -0.35 kg/week and body fat by -0.2 percentage points/week for 16 weeks.
General formula: W_k = W_0+k Delta_Wp_k = clamp(p_0+k Delta_p,0,70)LM_k = W_k(1-p_k/100)FM_k = W_k p_k/100Delta_LM = LM_N-LM_0Delta_FM = FM_N-FM_0 Weight and percentage-point changes are applied separately. Each week then partitions projected weight into lean and fat mass.
What each symbol means
Worked substitution with the default inputs
The default ends at 76.4 kg, 20.8% body fat, 60.509 kg lean mass, and 15.891 kg fat mass.
Purpose-built visual
Lean-and-fat stacked area trend
The full body-weight area is divided into lean and fat components across every projected week.
Worked situations
Practical examples
- The default starts at 82 kg and 24%, changes weight by -0.35 kg/week and body fat by -0.2 percentage points/week for 16 weeks.
- The default ends at 76.4 kg, 20.8% body fat, 60.509 kg lean mass, and 15.891 kg fat mass.
Better inputs
Useful tips
- Change one input at a time and confirm both the result and visual move.
- Keep the units stated beside every field.
- Retain intermediate precision and round only the reported result.
Before relying on the result
Limitations and common mistakes
- Linear body-composition trends are illustrative.
- Measurement error, hydration, glycogen, illness, training, and nutrition are not modeled.
- This is not medical advice.
Reference
Key terms
- Percentage point
- Arithmetic difference between two percentages.
- Lean mass
- Projected weight minus projected fat mass.
- Reconciliation
- Lean change plus fat change equals weight change.
Important note
Calculated from the entered measurements using the displayed method. It is a general reference and does not replace diagnosis or individualized professional guidance.
Frequently asked questions
Why not compound weight change?
The input is a fixed kg/week change.
Is -0.2% multiplicative?
No. It is percentage points per week.
Do components sum to weight?
Yes.
Is the trend a forecast?
It is an arithmetic scenario.