Calculate your medically estimated ideal weight using standard formulas
Male
Female
Biological sex affects bone mass and muscle distribution assumptions.
Enter your height in centimeters (e.g., 175).
Please enter a valid height between 100cm and 250cm.
Medium Frame (Standard)
Small Frame (-10%)
Large Frame (+10%)
Adjusts the calculation for bone structure.
Estimated Ideal Weight
70.0kg
Based on the Devine Formula (1974), widely used for medical dosing.
Formula / Method
Result (kg)
Description
What is an Ideal Body Weight in Kg Calculator?
An ideal body weight in kg calculator is a specialized tool designed to estimate a healthy weight target based on height and gender. Unlike simple BMI calculators that provide a broad range, ideal body weight (IBW) formulas attempt to pinpoint a specific weight value that is statistically associated with maximum longevity and lowest health risks.
These calculators are frequently used in medical settings for determining drug dosages, assessing nutritional needs, and setting realistic fitness goals. While no single number fits everyone, understanding your ideal body weight in kg provides a solid baseline for health planning.
It is important to note that "ideal" in this context refers to a statistical average derived from population studies, not necessarily an aesthetic ideal. Athletes with high muscle mass may weigh more than their calculated IBW while remaining perfectly healthy.
Ideal Body Weight Formulas and Mathematical Explanation
Over the decades, researchers have developed several formulas to calculate ideal body weight. Our calculator utilizes the four most respected methods. All formulas primarily rely on height over 5 feet (60 inches).
1. Devine Formula (1974)
Originally developed to calculate drug clearances, this is the most widely used formula in the medical community.
Men: 50 kg + 2.3 kg per inch over 5 feet
Women: 45.5 kg + 2.3 kg per inch over 5 feet
2. Robinson Formula (1983)
A modification of the Devine formula, often considered more accurate for modern populations.
Men: 52 kg + 1.9 kg per inch over 5 feet
Women: 49 kg + 1.7 kg per inch over 5 feet
3. Miller Formula (1983)
This variation often yields lower weight estimates and is sometimes used to establish a minimum healthy weight.
Men: 56.2 kg + 1.41 kg per inch over 5 feet
Women: 53.1 kg + 1.36 kg per inch over 5 feet
4. Hamwi Formula (1964)
Known as the "Rule of Thumb" method, it is simple and effective for quick estimations.
Men: 48 kg + 2.7 kg per inch over 5 feet
Women: 45.5 kg + 2.2 kg per inch over 5 feet
Variables Table
Variable
Meaning
Unit
Typical Range
Base Weight
Starting weight for 5ft height
kg
45.5 – 56.2 kg
Height Factor
Weight added per inch > 5ft
kg/inch
1.36 – 2.7 kg
Frame Adjustment
Correction for bone size
%
±10%
Practical Examples (Real-World Use Cases)
Example 1: The Average Male
Scenario: John is a 30-year-old male, 180 cm tall (approx. 5ft 11in), with a medium frame. He wants to know his target weight for a marathon.
Input: Male, 180 cm.
Calculation (Devine): 5ft 11in is 11 inches over 5ft. Formula: 50 + (2.3 × 11) = 50 + 25.3 = 75.3 kg.
Result: John's ideal body weight in kg is approximately 75.3 kg.
Interpretation: This gives John a specific target. If he currently weighs 85 kg, he might aim to lose weight gradually to reach this efficient running weight.
Example 2: The Petite Female
Scenario: Sarah is a female, 160 cm tall (approx. 5ft 3in), with a small frame.
Input: Female, 160 cm, Small Frame.
Calculation (Robinson): 5ft 3in is 3 inches over 5ft. Base Formula: 49 + (1.7 × 3) = 49 + 5.1 = 54.1 kg.
Frame Adjustment: Small frame reduces the target by 10%. 54.1 kg – 5.4 kg = 48.7 kg.
Result: Sarah's adjusted ideal body weight is roughly 48.7 kg.
Interpretation: Without the frame adjustment, the standard formula might suggest a weight that is too heavy for her lighter bone structure.
How to Use This Ideal Body Weight in Kg Calculator
Select Gender: Choose biological sex. This determines the base weight and muscle mass assumptions in the formulas.
Enter Height: Input your height in centimeters. If you know your height in feet/inches, convert it first (1 foot = 30.48 cm).
Select Frame Size: If you have a wrist circumference significantly smaller or larger than average, adjust the frame size. Leave as "Medium" if unsure.
Review Results: The calculator displays the Devine result as the primary number, but check the table below it to see the range provided by other formulas.
Analyze the Chart: The bar chart visually compares the different formulas against the WHO Healthy BMI range (BMI 18.5 – 25), helping you see where the "Ideal" sits within the broader "Healthy" spectrum.
Key Factors That Affect Ideal Body Weight Results
While the ideal body weight in kg calculator provides a precise number, several biological and lifestyle factors influence what your true "best" weight is.
Muscle Mass: Muscle is denser than fat. An athlete may weigh 10kg more than their IBW but have a low body fat percentage and excellent health. The calculator does not account for body composition.
Bone Density (Frame Size): People with larger bone structures naturally weigh more. The "Frame Size" input helps adjust for this, typically by ±10%.
Age: As we age, a slightly higher body weight is often associated with better survival rates and resilience against illness. Strict adherence to IBW formulas from the 1970s may not be optimal for seniors.
Fat Distribution: Where you carry weight matters. Visceral fat (around organs) is riskier than subcutaneous fat. Two people with the same IBW can have different health risks based on fat distribution.
Hydration Levels: Daily weight fluctuates by 1-2 kg due to water retention. Never treat the IBW result as a fixed daily target, but rather as a long-term average.
Pregnancy and Lactation: These formulas are absolutely not applicable for pregnant or breastfeeding women, who have distinct nutritional and weight requirements.
Frequently Asked Questions (FAQ)
Is the ideal body weight the same as a healthy BMI?
Not exactly. BMI (Body Mass Index) provides a wide range (e.g., 60kg to 80kg) that is considered healthy. Ideal Body Weight (IBW) formulas try to pinpoint a specific number within that range (e.g., 70kg) that is statistically optimal. IBW is more specific but less flexible than BMI.
Which formula is the most accurate?
The Devine formula is the standard for medical dosing. However, the Robinson and Miller formulas were developed later to improve accuracy for modern populations. There is no single "perfect" formula; looking at the average of all four is often the best approach.
Why does the calculator ask for height in cm?
This is an ideal body weight in kg calculator. The metric system (cm/kg) is the global standard for medical and scientific calculations, reducing rounding errors that occur when converting back and forth from feet/inches.
What if my weight is far from the ideal result?
Don't panic. If you are very muscular, you will naturally be above the IBW. If you are overweight, use the IBW as a long-term guide, but set smaller, achievable goals (like losing 5-10% of current weight) first.
Does age affect the calculation?
Standard IBW formulas do not include age as a variable. However, medical consensus suggests that maintaining a weight slightly above the classic IBW is beneficial for individuals over 65.
Can I use this for children?
No. These formulas are strictly for adults (18+). Children and teenagers are still growing, and their weight should be assessed using pediatric growth charts, not adult IBW formulas.
How do I know my frame size?
A simple method is the wrist test. Wrap your thumb and middle finger around your opposite wrist. If they overlap, you likely have a small frame. If they touch, medium. If they don't meet, large.
Is 50 kg the minimum weight for men?
In the Devine formula, 50 kg is the base for a 5-foot male. However, shorter men would subtract weight for inches under 5 feet, though these linear formulas become less accurate for very short statures.