BMI calculator

The BMI Calculator computes your Body Mass Index and provides comprehensive health insights including metabolic rate, calorie needs, and goal tracking. Beyond a simple number, it shows where you fall on the BMI scale and helps you understand what it means for your health.

The input form collects your measurements. Some fields are optional but provide more personalized results.

1

Age (Optional)

Enter your age in years. This field is optional but enables more accurate metabolic rate calculations. The field has a calendar icon.

2

Gender (Optional)

Select Male or Female by clicking one of the buttons. Gender affects metabolic rate calculations. Leave unselected if you prefer not to specify.

3

Choose units - METRIC or IMPERIAL

Click METRIC for kilograms and centimeters, or IMPERIAL for pounds and inches. The active option is visually highlighted. Switch anytime - values will convert automatically.

4

Enter Weight

Type your weight in the Weight field. In metric mode, enter kilograms (e.g., "90"). In imperial mode, enter pounds.

5

Enter Height

Type your height in the Height field. In metric mode, enter centimeters (e.g., "185"). In imperial mode, enter inches.

6

View instant results

As soon as you enter weight and height, your BMI calculates instantly. No need to click a button - results appear automatically below the form.

7

Favorites tab

On the right edge of the screen, you'll find the Favorites tab (heart icon). Click it to add this tool to your favorites for quick access from the homepage.

BMI Calculator input form with all fields

Your BMI result appears in a prominent box. This box contains your BMI value, category, description, and a visual scale.

1

BMI value (large number)

Your calculated BMI appears as a large bold number (e.g., 26.3). This is your weight-to-height ratio.

2

Category name

Below the number, you see your category: Underweight, Normal, Overweight, or Obese. This tells you which range your BMI falls into.

3

Health description

A brief explanation of what your BMI category means. For example: Your BMI indicates that you are overweight. Consider lifestyle modifications including diet and exercise to reduce health risks.

4

Heart icon

A heart icon appears on the left side of the result box, indicating this is health-related information.

BMI result display with category and health description

Below your BMI result, a colorful horizontal bar shows where your BMI falls within the WHO classification ranges. This visual guide makes it easy to understand your result at a glance.

The result box has three action buttons on the right side:

Below the main result, you'll find 4 tabs that provide deeper insights into your health metrics:
• Health insights: Risk level, ideal weight, body fat estimate
• Metabolic rate: Calories for maintenance, loss, or gain
• Achievements & Goals: Track progress and earn badges
• BMI Chart: WHO classification reference table

Click any tab to switch views. The active tab is visually highlighted.

The Health insights tab shows personalized health metrics based on your BMI calculation.

1

Switch to Health insights tab

Click the Health insights tab (with a heart icon). This is usually the default tab after calculation.

2

View 4 health cards

You'll see 4 cards arranged in a row, each showing a different health metric derived from your BMI.

3

HEALTH RISK card

Shows your estimated health risk level based on BMI category:
• Low: Normal BMI range
• Increased: Underweight or Overweight
• High: Obese range

4

IDEAL WEIGHT card

Displays the healthy weight range for your height (e.g., 63.3 - 85.2 kg). This is the weight range that would give you a BMI between 18.5 and 24.9.

5

TO GOAL card

Shows how much weight change is needed to reach the healthy range. Example: Lose 4.8 kg or Gain 3.2 kg. If already in normal range, shows On target.

6

BODY FAT % card

Provides an estimated body fat percentage based on your BMI, age, and gender (e.g., 28.4%).

Note: This is an estimate - actual body fat requires specialized measurement.

Health insights tab with personalized health metrics

The Metabolic rate tab calculates your daily calorie needs for maintenance, weight loss, or weight gain. You must select an activity level for accurate results.

1

Switch to Metabolic rate tab

Click the Metabolic rate tab (with a fire icon). The tab highlights orange when active.

2

Select Activity level

At the top, you'll see 5 activity level options. Click one to select it (the selected option is visually highlighted).

3

Activity level options

Choose the option that best describes your typical week:
• Sedentary: Little/no exercise (desk job)
• Light: 1-3 days/week exercise
• Moderate: 3-5 days/week exercise
• Active: 6-7 days/week exercise
• Very active: Physical job or intense training

4

BMR card

Basal Metabolic Rate (e.g., 1813 kcal/day) - calories your body burns at complete rest, just to maintain basic functions like breathing and circulation.

5

TDEE card

Total Daily Energy Expenditure (e.g., 2176 kcal/day) - total calories burned including activity. This is your maintenance level - eating this amount keeps weight stable.

6

WEIGHT LOSS card

Shows calories for safe weight loss (e.g., 1676 kcal/day). Based on -0.5 kg/week deficit (500 kcal/day below TDEE). A healthy, sustainable rate.

7

WEIGHT GAIN card

Shows calories for healthy weight gain (e.g., 2676 kcal/day). Based on +0.5 kg/week surplus (500 kcal/day above TDEE). Good for muscle building.

Metabolic rate tab with activity level selector and calorie targets

The Achievements & Goals tab gamifies your health tracking with badges and allows you to set weight goals.

1

Switch to Achievements & Goals tab

Click the Achievements & Goals tab (with a trophy icon). The tab has green text when active.

2

Goals & Progress section

At the top, you see your WEIGHT GOAL card with a progress bar showing current weight → target weight. Click SET GOAL button to set a target.

3

Tracking statistics

Three stat cards show your usage:
• CALCULATIONS: Total BMI calculations made (e.g., 67)
• DAYS TRACKING: Days you've used the calculator
• CURRENT STREAK: Consecutive days of tracking

4

Your badges section

Below the stats, you see 10 achievement badges arranged in 2 rows. Green badges are unlocked (earned). Gray badges are still locked.

5

Calculation badges

Earned by calculating BMI repeatedly:
• First Step: First BMI calculation
• Early Bird: 5 calculations
• Dedicated: 10 calculations
• Health Enthusiast: 25 calculations
• BMI Champion: 50 calculations

6

Streak badges

Earned by consistent daily tracking:
• 3-Day Streak: 3 consecutive days
• Week Warrior: 7 consecutive days

7

Goal badges

Earned by setting and achieving goals:
• In the Zone: Achieve healthy BMI range
• Goal Setter: Set your first weight goal
• Goal Achiever: Reach your weight goal

Achievements & Goals tab with badges and goal tracking

You can set a target weight to track your progress over time. The tool remembers your goal and shows progress toward it.

1

Open the Set Goal modal

On the Achievements & Goals tab, click the orange SET GOAL button in the top right corner. A modal window appears.

2

Enter Target weight

In the Target weight field, type your goal weight. The unit (kg or lb) matches your current selection (metric or imperial).

3

Confirm your goal

Click the orange SET GOAL button to save. Or click CANCEL to close without saving.

Set Goal modal for entering target weight

4

Track your progress

After setting a goal, the WEIGHT GOAL card shows your current weight, target weight, and a progress bar filling as you get closer to your goal.

Track your progress toward your weight goal

5

Delete your goal

To remove a goal, click the trash icon next to the SET GOAL button. This clears your target and resets the progress display.

Delete your goal using the trash icon

The BMI Chart tab displays the official WHO BMI classification table for reference.

1

Switch to BMI Chart tab

Click the BMI Chart tab (with a chart icon). You'll see a reference table.

2

Table structure

The table has 3 columns: CLASSIFICATION, BMI RANGE, and HEALTH RISK. Each row represents one BMI category.

3

Read the classifications

The 4 rows show WHO BMI categories for adults:
• Underweight (cyan text): < 18.5 → Increased risk
• Normal weight (green text): 18.5 - 24.9 → Low risk
• Overweight (orange text): 25.0 - 29.9 → Increased risk
• Obese (red text): ≥ 30.0 → High risk

4

Use as reference

This table is the same WHO classification used worldwide. Use it to understand the standard categories and their associated health risks.

BMI Chart with WHO classification reference