BMI Weight Loss Calculator

The BMI weight loss calculator is a goal-setting health tool that calculates your current Body Mass Index (BMI) and BMI Prime, then uses a target BMI you enter to calculate the exact target weight you need to reach that goal. It bridges the gap between knowing your current BMI and understanding what weight change is needed to get there.

What Is a BMI Weight Loss Calculator?

A BMI weight loss calculator is a tool that uses your height and weight to calculate your current BMI, then works backwards from a desired target BMI to return the goal weight you need to achieve. It uses the standard BMI formula in both directions — calculating current status and projecting a target weight — making it a practical tool for setting measurable, BMI-based weight loss goals.

Key Limitations

• BMI does not account for muscle mass or body composition — a highly muscular person may have a high BMI without excess fat

• It is a screening tool, not a diagnostic one — results should be reviewed with a healthcare provider for personalized guidance

The BMI Formulas

Current BMI

Weight (kg) ÷ [Height (m)]² = BMI

Target Weight from Target BMI

Target BMI × [Height (m)]² = Target Weight (kg)

For example: a person who is 170 cm (1.70 m) tall with a target BMI of 22 needs a target weight of 22 × (1.70)² = 22 × 2.89 = 63.6 kg.

BMI Prime

BMI ÷ 25 = BMI Prime

A BMI Prime below 1.0 is within or below the healthy range; above 1.0 indicates overweight or obese categories.

How the BMI Weight Loss Calculator Works

Current BMI Inputs

• Height — your current height (unit: cm)

• Weight — your current weight (unit: kg)

Current BMI Outputs

• BMI — auto-calculated current Body Mass Index

• BMI Prime — auto-calculated ratio of your BMI to 25

Target BMI and Weight Loss Section

• Target BMI — enter your desired BMI goal

• Target BMI Prime — auto-calculated from target BMI

• Target weight — auto-calculated weight needed to achieve your target BMI (kg)

How to Use the BMI Weight Loss Calculator — Step by Step

Example 1: Setting a Healthy BMI Goal

Height = 170 cm (1.70 m). Current weight = 80 kg. Target BMI = 24.9.

Step 1: Current BMI = 80 ÷ (1.70)² = 80 ÷ 2.89 = 27.7 (overweight). Step 2: Current BMI Prime = 27.7 ÷ 25 = 1.11. Step 3: Target weight = 24.9 × 2.89 = 71.96 kg. Step 4: Weight to lose = 80 − 71.96 = 8.04 kg.

Enter: Height = 170, Weight = 80, Target BMI = 24.9. Result: Target weight ≈ 72 kg.

Example 2: Reaching the Ideal Midpoint

Height = 165 cm (1.65 m). Current weight = 75 kg. Target BMI = 22.

Step 1: Current BMI = 75 ÷ (1.65)² = 75 ÷ 2.7225 = 27.5 (overweight). Step 2: Target weight = 22 × 2.7225 = 59.9 kg. Step 3: Weight to lose = 75 − 59.9 = 15.1 kg.

Enter: Height = 165, Weight = 75, Target BMI = 22. Result: Target weight ≈ 59.9 kg.

BMI Weight Status Reference Table

Note: Target BMI of 18.5–24.9 is the standard healthy range. Set your target BMI within this range for a medically recommended weight loss goal.

Frequently Asked Questions

How do I use target BMI to calculate my goal weight?

Enter your height and current weight to get your BMI, then type your desired target BMI in the Target BMI field. The calculator instantly returns the exact weight you need to reach that BMI.

What target BMI should I aim for?

The standard healthy BMI range is 18.5 to 24.9 — setting a target within this range gives you a medically recognized weight goal. A target of 22 is a commonly used midpoint for healthy weight management.

What is the difference between BMI and BMI Prime?

BMI is your raw Body Mass Index calculated from height and weight. BMI Prime divides your BMI by 25 — a value above 1.0 means you are above the healthy upper boundary, making it easy to see how far you are from your goal.

How much weight do I need to lose to lower my BMI by 1 point?

Lowering BMI by 1 point requires losing approximately [Height (m)]² kg. For a person 170 cm tall, that is (1.70)² = 2.89 kg of weight loss per BMI point. Use the calculator's target weight output to see the exact amount for your height.