FreeKit is a collection of free online tools for developers, SEO professionals, designers, students, content creators, and everyday users.

Are all tools completely free?

Yes. Every tool on FreeKit is free to use without subscriptions or hidden charges.

Do I need to create an account?

No. You can use all tools instantly without creating an account.

No. Most tools process data locally in your browser, and we do not permanently store your inputs.

Can I use FreeKit on mobile devices?

Yes. Every tool is fully responsive and works on smartphones, tablets, laptops, and desktop computers.

How often are new tools added?

We regularly add new tools and improve existing ones based on user feedback and industry needs.

Which browsers are supported?

FreeKit supports all modern browsers, including Chrome, Edge, Firefox, Safari, and other Chromium-based browsers.

Can I share these tools with others?

Absolutely. You are welcome to share FreeKit with friends, colleagues, students, and your team.

What is BMI and how is it calculated?

BMI (Body Mass Index) is a numerical value calculated from your weight and height. The formula is BMI = weight (kg) / height (m)². For imperial units, it is BMI = (weight in lbs × 703) / (height in inches)². It provides a simple screening measure to categorize individuals as underweight, normal weight, overweight, or obese. Our BMI Calculator handles the math for you instantly.

What are the BMI categories and their ranges?

The World Health Organization (WHO) classifies BMI into four main categories: Underweight is a BMI below 18.5, Normal weight ranges from 18.5 to 24.9, Overweight is between 25.0 and 29.9, and Obese is a BMI of 30.0 or higher. These ranges apply to adults aged 20 and older. Our calculator color-codes each category so you can instantly see where your result falls on the scale.

Is BMI accurate for everyone?

BMI is a useful screening tool but it has limitations. It does not distinguish between muscle mass and fat mass, so athletes or individuals with high muscle mass may have a high BMI without excess body fat. It also does not account for age, sex, ethnicity, or body fat distribution. For a more complete picture of health, BMI should be used alongside other measurements like waist circumference, body fat percentage, and consultation with a healthcare provider.

Does BMI apply differently to men and women?

The standard BMI formula and categories are the same for adult men and women. However, women naturally tend to have more body fat than men at the same BMI value. Despite this, the WHO categories are universally applied for simplicity. Some health organizations suggest that women may have a slightly higher healthy BMI threshold, but the standard ranges (18.5–24.9 for normal) remain the most widely used reference.

How do I convert between metric and imperial units for BMI?

To convert height: 1 inch = 2.54 cm, and 1 foot = 12 inches. To convert weight: 1 kg = 2.20462 lbs. Our calculator has a built-in unit toggle — simply switch between Metric (cm/kg) and Imperial (ft+in/lbs) and the conversion is handled automatically. No manual math needed. If you prefer to do it yourself, our Unit Converter can help with individual conversions.

What is a healthy BMI for my height?

A healthy BMI is between 18.5 and 24.9 regardless of height. However, you can convert this to a healthy weight range for your specific height. For example, a person who is 170 cm (5'7") tall has a healthy weight range of approximately 53.5 kg to 72.0 kg (118 lbs to 159 lbs). Our calculator displays your personalized healthy weight range based on the height you enter, making it easy to see your target zone.

Can BMI be used for children and teens?

Standard BMI categories do not apply to children and teens (ages 2–19). Instead, health professionals use BMI-for-age percentiles, which compare a child's BMI to other children of the same age and sex. A BMI at the 85th to 94th percentile is considered overweight, and at or above the 95th percentile is considered obese. This calculator is designed for adults (20+). For children, consult a pediatrician.

How often should I check my BMI?

For most adults, checking your BMI once every few months is sufficient unless you are actively trying to gain or lose weight, in which case monthly checks can help track progress. Remember that BMI is just one health indicator — it does not replace regular health check-ups, blood work, or body composition assessments. Consistent trends in your BMI over time are more meaningful than any single measurement.

What should I do if my BMI is outside the normal range?

If your BMI falls outside the 18.5–24.9 range, do not panic. First, consider factors like muscle mass that may affect the result. If you believe excess body fat is a concern, consult a healthcare professional for personalized advice. They may recommend dietary changes, exercise plans, or further assessments. For weight management, our Percentage Calculator can help track body fat percentage changes.

Is my BMI data stored or sent anywhere?

No. This BMI calculator runs entirely in your browser. Your height, weight, and calculated BMI are never sent to any server, stored in any database, or shared with anyone. As soon as you close or refresh the page, all entered data disappears. Your health information stays completely private.

BMI Calculator

Calculate your Body Mass Index based on height and weight.

BeginnerCalculatorsFreev1.0.0Updated Jul 22, 2025

BMI Calculator

Enter your height and weight to calculate your Body Mass Index

Unit System

Metric (cm/kg)Imperial (ft/lbs)

Height

Weight

100% Private — Runs in Your Browser

All BMI calculations happen locally using JavaScript. Your height, weight, and results are never sent to any server, stored, or shared. Close the tab and your data is gone.

How to Use the BMI Calculator

Calculating your BMI takes just a few seconds. Follow these steps:

Choose your unit system — Toggle between Metric (centimeters and kilograms) and Imperial (feet/inches and pounds) using the switch at the top.
Enter your height — Type your height in centimeters (e.g., 175) or in feet and inches (e.g., 5 ft 9 in).
Enter your weight — Type your weight in kilograms or pounds.
Click Calculate BMI — Your BMI value, category, healthy weight range, and health tips appear instantly.
Review the visual gauge — The color-coded scale shows exactly where your BMI falls relative to each category.

BMI Categories Explained

The World Health Organization (WHO) classifies BMI into four main categories for adults:

Underweight (BMI < 18.5)

A BMI below 18.5 suggests that a person may be underweight. This can indicate insufficient nutrition, an underlying medical condition, or an overly high metabolism. Being underweight is associated with risks such as weakened immunity, bone loss, and fertility issues.

Normal Weight (18.5 – 24.9)

A BMI between 18.5 and 24.9 is considered within the normal or healthy weight range. People in this range generally have a lower risk of weight-related health problems such as heart disease, type 2 diabetes, and certain cancers.

Overweight (25.0 – 29.9)

A BMI between 25.0 and 29.9 indicates overweight. Carrying excess weight increases the risk of developing conditions like high blood pressure, elevated cholesterol, type 2 diabetes, and cardiovascular disease. Lifestyle changes can often help.

Obese (BMI ≥ 30.0)

A BMI of 30.0 or higher is classified as obese. Obesity is linked to significantly increased risks of serious health conditions including heart disease, stroke, type 2 diabetes, sleep apnea, and certain cancers. Medical guidance is strongly recommended.

How BMI Is Calculated

Metric Formula

BMI = weight (kg) ÷ height (m)²

For example, if you weigh 70 kg and are 1.75 m tall: BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 (Normal).

Imperial Formula

BMI = (weight (lbs) × 703) ÷ height (in)²

For example, if you weigh 154 lbs and are 69 inches tall: BMI = (154 × 703) ÷ (69 × 69) = 108262 ÷ 4761 = 22.7 (Normal).

Limitations of BMI

While BMI is a widely used screening tool, it has important limitations to be aware of:

Does not measure body fat directly — BMI uses only height and weight, so it cannot distinguish between fat mass and lean mass (muscle, bone, water).
Inaccurate for athletes — People with high muscle mass (e.g., bodybuilders) may have a high BMI without excess body fat.
Ignores fat distribution — Visceral fat (around organs) is more dangerous than subcutaneous fat, but BMI does not differentiate between them.
Not age- or sex-specific for adults — The same formula applies to all adults, though body composition naturally varies by age and sex.
Ethnic variations exist — Some populations may face health risks at lower BMI thresholds. WHO has suggested modified cut-offs for Asian populations.
Not for children or teens — BMI percentiles (not absolute values) are used for ages 2–19, and require age- and sex-specific growth charts.

Tips for Maintaining a Healthy BMI

Eat a balanced diet — Focus on whole foods: vegetables, fruits, lean proteins, whole grains, and healthy fats. Limit processed foods and added sugars.
Stay active — Aim for at least 150 minutes of moderate aerobic activity (brisk walking, cycling) or 75 minutes of vigorous activity (running, swimming) per week.
Get enough sleep — Poor sleep is linked to weight gain. Adults should aim for 7–9 hours of quality sleep each night.
Monitor your weight regularly — Weekly weigh-ins help you catch trends early. Use our Percentage Calculator to track weight change percentages.
Manage stress — Chronic stress elevates cortisol, which can promote fat storage, especially around the abdomen. Practice mindfulness, yoga, or deep breathing.
Stay hydrated — Drinking water before meals can help control appetite. Aim for at least 8 glasses (2 liters) of water daily.

BMI in Different Contexts

For Health Insurance

Many health insurance companies use BMI as one factor in determining premiums. A higher BMI may lead to higher premiums in some regions, as it is associated with increased health risks. Maintaining a healthy BMI can have financial benefits beyond just health.

For Sports and Fitness

Athletes and fitness enthusiasts should be cautious about relying solely on BMI. A rugby player or weightlifter may have a BMI in the “overweight” or “obese” range due to muscle mass. Body fat percentage or waist-to-hip ratio may be more meaningful metrics in these cases.

For Pregnancy

Pre-pregnancy BMI is used to recommend healthy weight gain during pregnancy. Women with a normal BMI are advised to gain 11.5–16 kg, while underweight women may be advised to gain more. Always consult an obstetrician for personalized guidance.

For Children and Teens

For individuals aged 2–19, BMI is interpreted using age- and sex-specific percentile charts from the CDC. A child at the 5th percentile is considered underweight, while a child at or above the 95th percentile is considered obese. Standard adult BMI categories do not apply.

Other Useful Calculators

Complement your health and finance calculations with these free tools:

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Calculate percentages, increases, decreases, and differences — useful for tracking weight change percentages.

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Split restaurant bills with custom tip percentages and per-person amounts.

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Calculate final prices after discounts and sales tax — great for health product shopping.

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Calculate monthly loan payments, total interest, and amortization schedules for any loan.

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How to Use the BMI Calculator

Calculating your BMI takes just a few seconds. Follow these steps:

Choose your unit system — Toggle between Metric (centimeters and kilograms) and Imperial (feet/inches and pounds) using the switch at the top.

Enter your height — Type your height in centimeters (e.g., 175) or in feet and inches (e.g., 5 ft 9 in).

Enter your weight — Type your weight in kilograms or pounds.

Click Calculate BMI — Your BMI value, category, healthy weight range, and health tips appear instantly.

Review the visual gauge — The color-coded scale shows exactly where your BMI falls relative to each category.

BMI Categories Explained

The World Health Organization (WHO) classifies BMI into four main categories for adults:

Underweight (BMI < 18.5)

Normal Weight (18.5 – 24.9)

Overweight (25.0 – 29.9)

Obese (BMI ≥ 30.0)

How BMI Is Calculated

Metric Formula

BMI = weight (kg) ÷ height (m)²

For example, if you weigh 70 kg and are 1.75 m tall: BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 (Normal).

Imperial Formula

BMI = (weight (lbs) × 703) ÷ height (in)²

For example, if you weigh 154 lbs and are 69 inches tall: BMI = (154 × 703) ÷ (69 × 69) = 108262 ÷ 4761 = 22.7 (Normal).

Limitations of BMI

While BMI is a widely used screening tool, it has important limitations to be aware of:

Does not measure body fat directly — BMI uses only height and weight, so it cannot distinguish between fat mass and lean mass (muscle, bone, water).

Inaccurate for athletes — People with high muscle mass (e.g., bodybuilders) may have a high BMI without excess body fat.

Ignores fat distribution — Visceral fat (around organs) is more dangerous than subcutaneous fat, but BMI does not differentiate between them.

Not age- or sex-specific for adults — The same formula applies to all adults, though body composition naturally varies by age and sex.

Ethnic variations exist — Some populations may face health risks at lower BMI thresholds. WHO has suggested modified cut-offs for Asian populations.

Not for children or teens — BMI percentiles (not absolute values) are used for ages 2–19, and require age- and sex-specific growth charts.

Tips for Maintaining a Healthy BMI

Eat a balanced diet — Focus on whole foods: vegetables, fruits, lean proteins, whole grains, and healthy fats. Limit processed foods and added sugars.

Stay active — Aim for at least 150 minutes of moderate aerobic activity (brisk walking, cycling) or 75 minutes of vigorous activity (running, swimming) per week.

Get enough sleep — Poor sleep is linked to weight gain. Adults should aim for 7–9 hours of quality sleep each night.

Monitor your weight regularly — Weekly weigh-ins help you catch trends early. Use our Percentage Calculator to track weight change percentages.

Manage stress — Chronic stress elevates cortisol, which can promote fat storage, especially around the abdomen. Practice mindfulness, yoga, or deep breathing.

Stay hydrated — Drinking water before meals can help control appetite. Aim for at least 8 glasses (2 liters) of water daily.