Calculate Your Best Weight
Scientific Ideal Body Weight (IBW) Calculator
Male
Female
Biometric formulas vary by gender.
Enter height in feet and inches.
Please enter a valid height.
Enter height in centimeters.
Please enter a positive weight.
Small Frame (-10%)
Medium Frame
Large Frame (+10%)
Adjusts formula for bone structure.
Your Estimated Best Weight
166 lbs
Based on Devine Formula & Frame Size
Healthy BMI Range
129 – 174 lbs
Current BMI
25.8
Difference to Goal
-14 lbs
Comparison of Current Weight vs. Calculated Ideal Targets
| Metric | Value | Description |
|---|
What is Calculate Your Best Weight?
To calculate your best weight is to determine a medically referenced "Ideal Body Weight" (IBW) based on your unique physiological characteristics. Unlike a generic number on a scale, your best weight considers your height, gender, and skeletal frame size to suggest a target mass associated with maximum longevity and minimal risk of chronic disease.
This calculation is essential for:
- Individuals managing weight: Setting realistic, healthy goals rather than arbitrary ones.
- Medical dosing: Physicians often use IBW to determine medication dosages.
- Athletes: Establishing performance weight classes relative to height.
A common misconception is that "best weight" equals "lowest possible weight." In reality, falling below your ideal weight range can be just as detrimental to health as exceeding it. This tool helps you calculate your best weight using proven medical formulas.
Calculate Your Best Weight Formula and Explanation
Several formulas exist to calculate your best weight. This calculator primarily uses the Devine Formula (1974), which is widely regarded as the standard for medical use, adjusted for body frame size.
The Devine Formula
For Men: 50.0 kg + 2.3 kg per inch over 5 feet.
For Women: 45.5 kg + 2.3 kg per inch over 5 feet.
Frame Size Adjustment
Since bone density affects mass, we apply a correction factor:
- Small Frame: Subtract 10% from the formula result.
- Medium Frame: No adjustment.
- Large Frame: Add 10% to the formula result.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Base Weight | Starting constant for height of 5ft | kg | 45.5 (F) / 50.0 (M) |
| Height Factor | Weight added per inch over 60″ | kg/inch | 2.3 |
| Frame Factor | Adjustment for skeletal size | % | -10% to +10% |
Practical Examples
Example 1: The Average Male
Scenario: John is a 5'10" male with a medium frame.
- Base Calculation: 50 kg + (2.3 kg × 10 inches) = 73 kg.
- Conversion: 73 kg ≈ 161 lbs.
- Result: John's best weight is approximately 161 lbs. A healthy range would typically span 10-15 lbs around this target.
Example 2: The Tall Female with Small Frame
Scenario: Sarah is a 5'8″ female with a small frame.
- Base Calculation: 45.5 kg + (2.3 kg × 8 inches) = 63.9 kg.
- Frame Adjustment: Small frame reduces this by 10%. 63.9 kg – 6.39 kg = 57.51 kg.
- Conversion: 57.51 kg ≈ 127 lbs.
- Result: Sarah's calculated best weight is roughly 127 lbs, reflecting her lighter skeletal structure.
How to Use This Calculate Your Best Weight Calculator
- Select Your Unit System: Choose Imperial (lbs/ft) or Metric (kg/cm) based on your preference.
- Enter Biological Data: precise gender and height are critical as the base formulas differ significantly between men and women.
- Input Current Weight: This allows the tool to calculate the difference between your current state and your goal.
- Select Frame Size: If you can wrap your thumb and middle finger around your wrist and they overlap, select "Small". If they just touch, select "Medium". If they don't meet, select "Large".
- Analyze Results: Look at the "Estimated Best Weight" for a specific target, but reference the "Healthy BMI Range" for a broader, flexible window of health.
Key Factors That Affect Calculate Your Best Weight Results
When you calculate your best weight, understand that the number is a guideline, affected by several real-world financial and physical factors:
- Muscle Mass vs. Fat: Muscle is denser than fat. An athlete may weigh more than their "ideal" formula weight but be healthier than a sedentary person at the "correct" weight.
- Age: Metabolism slows with age. While the formula doesn't change, the maintenance of that weight becomes harder, often requiring adjusted caloric intake.
- Bone Density: Genetic variances in bone density (osteoporosis vs. high density) can skew scale weight by several pounds independent of body fat.
- Water Retention: Sodium intake and hydration levels can fluctuate daily weight by 1-5 lbs, masking your true "best weight."
- Health Conditions: Conditions like thyroid issues or diabetes may require a doctor to set a customized "best weight" that differs from standard formulas.
- Body Composition Goals: If your goal is bodybuilding, your "best weight" will be significantly higher than the Devine formula, which was derived for drug dosing, not aesthetics.
Frequently Asked Questions (FAQ)
Is the calculated best weight a strict rule?
No. It is a statistical average based on population data. A healthy weight is a range, not a single number.
Why does gender affect the calculation?
Biologically, men generally have higher muscle mass and bone density than women of the same height, leading to a higher baseline weight.
Does this calculator apply to children?
No. These formulas are intended for adults (18+). Children and teenagers are still growing, and their weight should be evaluated using CDC growth charts.
What if I am very muscular?
If you are an athlete or bodybuilder, the BMI and IBW formulas may classify you as overweight. In this case, Body Fat Percentage is a better metric than total weight.
How often should I calculate my best weight?
Your height and frame don't change, so your target number remains stable. However, you should check your progress against this number weekly if actively managing weight.
Can I change my frame size?
Frame size is determined by skeletal structure (wrist circumference) and does not change with weight loss or gain.
What is a healthy rate of weight change?
Most health experts recommend losing or gaining 1-2 lbs per week. Rapid changes can result in muscle loss or fat gain rather than healthy tissue changes.
Does age affect the formula?
Standard IBW formulas do not factor in age, but many doctors accept a slightly higher weight for older adults to provide a reserve against illness.