Ideal Weight Calculator

Not what the fashion industry says. Not what your friend weighs. What does the math say — based on your height, your sex, and your actual physiology?

An ideal body weight calculator answers that question using medically developed formulas — the same ones doctors and pharmacists use to calculate safe drug doses and clinical benchmarks.

Let's break it all down clearly.

What Is Ideal Body Weight (IBW)?

Ideal Body Weight (IBW) is the calculated weight associated with the lowest mortality risk for a given height, age, and sex.

Key things to understand about IBW:

• Originally derived from Metropolitan Life Insurance tables in the mid-20th century

• Used clinically to assess nutritional status and calculate medication dosages

• Represents a "healthy weight target" — not a vanity metric

• Based on height and sex — not age, ethnicity, or body composition

• Limitation: IBW doesn't distinguish between muscle and fat — a very muscular person may be "overweight" by IBW but perfectly healthy

IBW is best used as a clinical reference point, not a personal goal carved in stone.

Ideal Body Weight Formulas

There are three main IBW formulas used in clinical and health settings:

Devine Formula (Metric) — Most Widely Used

Men: IBW = 50 kg + 2.3 kg × (height in inches − 60)

Women: IBW = 45.5 kg + 2.3 kg × (height in inches − 60)

The Devine formula is the gold standard — used in hospitals worldwide for drug dosing and ventilator settings.

Hamwi Method (Imperial)

Men: IBW = 106 lbs + 6 lbs per inch over 5 feet

Women: IBW = 100 lbs + 5 lbs per inch over 5 feet

The Hamwi method is simpler and commonly used in quick clinical assessments.

Adjusted Body Weight (ABW)

For individuals who are significantly overweight, standard IBW underestimates their needs. Use:

ABW = IBW + 0.4 × (Actual Weight − IBW)

This adjusted formula gives a better estimate for nutritional planning and medication dosing in overweight or obese individuals.

How to Calculate Ideal Body Weight — Step by Step

Example 1 — Male, 5'10" (Devine Formula)

1. Height in inches = 70 inches

2. Inches over 5 feet = 70 − 60 = 10 inches

3. IBW = 50 + (2.3 × 10)

4. IBW = 50 + 23 = 73 kg

Example 2 — Female, 5'5" (Devine Formula)

1. Height in inches = 65 inches

2. Inches over 5 feet = 65 − 60 = 5 inches

3. IBW = 45.5 + (2.3 × 5)

4. IBW = 45.5 + 11.5 = 57 kg

IBW Calculator Inputs Explained

The body ideal weight calculator asks for:

• Sex — Male or Female (formulas differ by sex)

• Height — in cm or feet/inches

• Current weight — in kg or lbs (used for ABW if needed)

• Target BMI — defaults to 22 (the midpoint of the healthy BMI range of 18.5–24.9)

The default BMI of 22 is used when you want a simple healthy weight target without choosing a specific formula.

IBW by Height — Quick Reference Table

These are calculated estimates — always factor in body composition and consult a healthcare professional for clinical decisions.

For instant IBW calculation across all formulas and unit types, CalcyMate handles everything in seconds. Explore more free health calculators for BMI, calorie needs, body fat percentage, and more.

Fun Fact That'll Make You Laugh 😄

The Devine formula — used in hospitals worldwide to calculate drug doses — was originally published in 1974 in a paper about... predicting ideal weight for drug dosing purposes.

The author, Dr. B.J. Devine, basically made up the formula based on clinical judgment with no formal study behind it.

Hospitals still use it 50 years later. Your medication dose might be calculated from a number one doctor eyeballed in 1974. Sleep well. 😂

FAQs

How to calculate IBW if under 5 feet tall?

For people under 5 feet, the Devine formula is adjusted by subtracting rather than adding. For every inch below 5 feet, subtract 2.3 kg from the base weight. So for a woman who is 4'10" (2 inches below 5 feet): IBW = 45.5 − (2.3 × 2) = 45.5 − 4.6 = 40.9 kg. The same logic applies for men using the 50 kg base.

What is the ideal weight for 170 cm and 70 kg?

At 170 cm (approximately 5'7"), the Devine formula gives: Male IBW = 50 + (2.3 × 7) = 66.1 kg / Female IBW = 45.5 + (2.3 × 7) = 61.6 kg. At 70 kg, a male at 170 cm is very close to ideal weight. A female at 70 kg would be slightly above IBW but still within a healthy range depending on body composition. BMI at 170 cm / 70 kg = 24.2 — solidly within the healthy range of 18.5–24.9.

Is IBW the same as healthy weight?

Not exactly — IBW is a calculated clinical estimate, while "healthy weight" is a broader range. IBW gives one specific number, but healthy weight is typically expressed as a BMI range of 18.5–24.9, which covers a span of several kilograms. IBW is useful as a reference point, but it doesn't account for muscle mass, bone density, or ethnic variations in body composition.

What is the difference between IBW and ABW?

IBW (Ideal Body Weight) is the calculated target weight for your height and sex. ABW (Adjusted Body Weight) is used when someone's actual weight is significantly higher than their IBW. ABW formula: IBW + 0.4 × (Actual Weight − IBW). 

Why do doctors use IBW for drug dosing?

Because many drugs distribute based on lean body mass — not total body weight. Using actual weight in an obese patient could result in dangerously high doses of certain medications. IBW gives a standardized, consistent baseline — especially critical for drugs with narrow therapeutic windows like aminoglycoside antibiotics, chemotherapy agents, and heparin.