Ideal Body Weight Calculator

How to Calculate Ideal Body Weight

Calculating ideal body weight (IBW) is a method used to estimate a healthy weight range based on an individual's height, gender, and body frame. While there's no single "ideal" weight for everyone, these calculations provide a general guideline for a healthy weight range.

Ideal Body Weight Formulas

Several formulas are commonly used to calculate IBW:

1. Devine Formula:
   Male: IBW (kg) = 50 + 2.3 × (Height in inches - 60)
   Female: IBW (kg) = 45.5 + 2.3 × (Height in inches - 60)
2. Robinson Formula:
   Male: IBW (kg) = 52 + 1.9 × (Height in inches - 60)
   Female: IBW (kg) = 49 + 1.7 × (Height in inches - 60)
3. Miller Formula:
   Male: IBW (kg) = 56.2 + 1.41 × (Height in inches - 60)
   Female: IBW (kg) = 53.1 + 1.36 × (Height in inches - 60)
4. Hamwi Formula:
   Male: IBW (kg) = 48 + 2.7 × (Height in inches - 60)
   Female: IBW (kg) = 45.5 + 2.2 × (Height in inches - 60)

Calculation Steps

1. Convert height to inches if necessary (1 inch = 2.54 cm)
2. Choose the appropriate formula based on gender
3. Apply the formula using the height in inches
4. Adjust for body frame size (if applicable):
   • Small frame: Subtract 10%
   • Large frame: Add 10%
5. Calculate the average of all formulas for a more comprehensive estimate

Example Calculation

Let's calculate the IBW for a female who is 165 cm tall with a medium frame.

Step 1: Convert height to inches

$$\begin{align} 165 \text{ cm} \times \frac{1 \text{ inch}}{2.54 \text{ cm}} = 64.96 \text{ inches} \end{align}$$

Step 2: Apply the Devine Formula for females

$$\begin{align} IBW &= 45.5 + 2.3 \times (64.96 - 60) \\ &= 45.5 + 2.3 \times 4.96 \\ &= 45.5 + 11.408 \\ &= 56.908 \text{ kg} \end{align}$$

Step 3: No adjustment needed for medium frame

Step 4: Repeat for other formulas and calculate average

Robinson: 57.432 kg
Miller: 59.766 kg
Hamwi: 56.412 kg

Average IBW:

$$\begin{align} \frac{56.908 + 57.432 + 59.766 + 56.412}{4} = 57.63 \text{ kg} \end{align}$$

Therefore, the estimated ideal body weight for this person is approximately 57.63 kg (127 lbs).

Visual Representation

This bar chart compares the ideal body weight estimates from different formulas for the example calculation. It visually demonstrates how the various formulas produce slightly different results, and shows the average IBW as a comprehensive estimate.