Compare your current weight with ideal weight estimates from multiple medical formulas
These formulas provide estimates only. Actual healthy weight varies by body composition, muscle mass, and frame size.
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Faiq Ur Rahman is a web designer, digital product developer, and founder of Toolraxy, a growing platform of web-based calculators and utility tools. He specializes in building structured, user-friendly tools focused on health, finance, productivity, and everyday problem-solving.
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What does your “ideal weight” actually mean? Unlike a single number you might find on a generic chart, medical ideal weight formulas account for your height, gender, and frame size though frame estimation varies across methods. This ideal weight calculator applies four established medical formulas developed between 1964 and 1983, each with slightly different assumptions about healthy body composition.
The Robinson, Miller, Devine, and Hamwi formulas remain in use today for medication dosing, insurance assessments, and weight management goal setting. Rather than giving you one number, this calculator shows you the range of recommendations across all four methods plus the healthy BMI range for your height.
Powered by Toolraxy, this tool helps you understand where your current weight sits relative to evidence-based estimates. Enter your height, gender, and current weight to see ideal weight calculations in both kilograms and pounds. A clear comparison box shows exactly how far your current weight deviates from the average ideal weight across all formulas whether above, below, or right on target.
Select your gender — Choose Male or Female (formulas differ by sex)
Enter your height — Type your height and select the unit (cm, inches, meters, or feet)
Enter your current weight — Input your weight and choose kilograms (kg) or pounds (lbs)
Click Calculate — Results update automatically as you type, or press the Calculate button
Review the healthy BMI range — See the weight range corresponding to BMI 18.5–24.9
Check each formula estimate — Compare Robinson, Miller, Devine, and Hamwi results
View the average ideal weight — See the mean of all four formulas
Read the comparison box — Understand how your current weight compares to the average ideal
The Ideal Weight Calculator uses height in inches above 5 feet (60 inches) as the primary variable, with gender-specific starting weights and multipliers. All heights convert to inches internally.
Height conversion to inches:
Centimeters (cm) to inches: divide by 2.54
Meters (m) to inches: multiply by 39.37
Feet (ft) to inches: multiply by 12
Inches (in): no conversion needed
Calculation of “extra inches over 5 feet”:
Extra Inches = Height in inches − 60
If height is less than 5 feet (60 inches), extra inches = 0.
Weight conversion for display:
Kilograms to pounds: multiply by 2.20462
Pounds remain as entered for current weight
All formulas produce results in kilograms (kg).
Robinson Formula (1983)
Female: 49 kg + (1.7 kg × extra inches over 5 ft)
Miller Formula (1983)
Female: 53.1 kg + (1.36 kg × extra inches over 5 ft)
Devine Formula (1974)
Female: 45.5 kg + (2.3 kg × extra inches over 5 ft)
Hamwi Formula (1964)
Female: 45.5 kg + (2.2 kg × extra inches over 5 ft)
BMI 18.5 lower bound = 18.5 × (Height in meters)² BMI 24.9 upper bound = 24.9 × (Height in meters)²
The calculator compares your current weight (converted to kg) to the average ideal weight (mean of all four formulas):
| Difference | Display | Box Color |
|---|---|---|
| Less than ±1 kg | “Your current weight is right at the average ideal weight” | Green |
| Positive (above) | “X kg above average ideal weight” | Red |
| Negative (below) | “X kg below average ideal weight” | Green |
| Scenario | Behavior |
|---|---|
| Height ≤ 0 | All results show “—”; BMI range shows “—” |
| Height under 5 ft (60 inches) | Extra inches = 0 for all formulas |
| Current weight ≤ 0 | Comparison box prompts user to enter weight |
| Current weight valid | Displays in kg and lbs with comparison |
Scenario: A 35-year-old female is 165 cm tall and weighs 68 kg. She wants to understand her ideal weight range using established medical formulas.
Step-by-step calculation:
Convert height to inches — 165 cm ÷ 2.54 = 65 inches
Calculate extra inches over 5 ft — 65 − 60 = 5 inches
Calculate Robinson (female) — 49 kg + (1.7 × 5) = 49 + 8.5 = 57.5 kg
Calculate Miller (female) — 53.1 kg + (1.36 × 5) = 53.1 + 6.8 = 59.9 kg
Calculate Devine (female) — 45.5 kg + (2.3 × 5) = 45.5 + 11.5 = 57.0 kg
Calculate Hamwi (female) — 45.5 kg + (2.2 × 5) = 45.5 + 11.0 = 56.5 kg
Calculate average ideal weight — (57.5 + 59.9 + 57.0 + 56.5) ÷ 4 = 230.9 ÷ 4 = 57.7 kg
Calculate healthy BMI range — Height in meters = 1.65 m; BMI 18.5 = 18.5 × 2.7225 = 50.4 kg; BMI 24.9 = 24.9 × 2.7225 = 67.8 kg
Compare current weight (68 kg) to average ideal (57.7 kg) — 68 − 57.7 = 10.3 kg above average
Interpretation: The user’s current weight of 68 kg is 10.3 kg above the average ideal weight of 57.7 kg from the four formulas. Her weight sits at the upper edge of the healthy BMI range (67.8 kg is the upper limit of 24.9 BMI). This suggests she is close to the healthy weight boundary. The variation between formulas (56.5–59.9 kg) reflects different methodological assumptions — all converge around the 57–60 kg range for her height.
The most frequent error is measuring height incorrectly — not standing fully straight, measuring in shoes (adds 1-2 inches), or rounding height down. Another common mistake is using the wrong gender base values — men and women have different starting weights and multipliers. Forgetting that formulas assume medium frame leads to unrealistic expectations for large or small frame individuals. Comparing current weight against a single formula rather than the average ideal weight ignores normal formula variation. Finally, assuming ideal weight formulas apply to athletes or very muscular individuals — these formulas were derived from general populations and will underestimate healthy weight for muscular people.
A 45-year-old male, 178 cm tall (70 inches), current weight 85 kg, consults his doctor about weight management. The calculator shows: extra inches = 10; Robinson = 52 + (1.9 × 10) = 71 kg; Miller = 56.2 + (1.41 × 10) = 70.3 kg; Devine = 50 + (2.3 × 10) = 73 kg; Hamwi = 48 + (2.7 × 10) = 75 kg; average ideal weight = 72.3 kg. Healthy BMI range for 1.78m: 18.5 × 3.1684 = 58.6 kg to 24.9 × 3.1684 = 78.9 kg. Current weight 85 kg exceeds both ideal formulas (by ~13 kg) and the healthy BMI upper limit (78.9 kg) by 6.1 kg. The comparison box shows “Your current weight is 12.7 kg above the average ideal weight.” This patient uses the healthy BMI upper limit (79 kg) as his initial goal, representing a 6 kg loss, rather than trying to reach 72 kg which might be unrealistic for his muscular frame.
Saves time — Four formulas calculated instantly with unit conversion
Multiple medical references — Includes Robinson, Miller, Devine, and Hamwi
Healthy BMI range included — See clinical guidelines alongside formula estimates
Clear comparison — Color-coded box shows how current weight compares to average ideal
Free to use — No premium version, subscriptions, or registration
Private — All calculations in your browser; no data transmitted
Accessible on any device — Works on phones, tablets, and computers
Dual units — Results display in both kilograms and pounds
Shareable results — Copy or share ideal weight data for medical appointments
Ideal weight formulas provide population estimates, not individual prescriptions. Accuracy varies by frame size, muscle mass, and ethnicity. For medium-framed sedentary adults, formulas typically predict weights within 5-10% of healthy ranges. For athletes, muscular individuals, or large frames, formulas underestimate by 5-15%.
Devine (1974) is most common for medication dosing, particularly for calculating creatinine clearance and drug doses. For general weight counseling, many doctors reference the healthy BMI range (18.5–24.9) rather than these older formulas. Always discuss specific formula selection with your healthcare provider for clinical decisions.
Ideal weight comes from formulas based on height and gender. Target weight is a personalized goal set with a healthcare provider considering frame size, muscle mass, age, and medical conditions. A muscular person may have a target weight well above formula ideal weight. A older adult may have a target weight below formula ideal weight.
Yes, as a starting point. The healthy BMI range provides evidence-based boundaries. The average ideal weight from all four formulas offers a reasonable reference. However, set realistic goals with professional guidance — losing from 85 kg to 72 kg (average ideal) may be appropriate for some but unrealistic or unnecessary for others depending on body composition.
Yes, significantly. Athletic individuals with above-average muscle mass will exceed formula ideal weights while remaining perfectly healthy. The calculator does not account for muscle — interpret results accordingly. Bodybuilders and strength athletes should focus on body fat percentage rather than ideal weight formulas.
Calculate your height in meters, then multiply by itself to get height squared. Multiply by 18.5 for the lower bound, by 24.9 for the upper bound. For 170 cm: 1.7 × 1.7 = 2.89; 18.5 × 2.89 = 53.5 kg; 24.9 × 2.89 = 72.0 kg. This calculator displays this range automatically.
Each formula uses different base weights and per-inch multipliers based on different research populations. Variation of 2-5 kg at average heights is normal. The average of all four formulas smooths out individual biases. For medication dosing, stick to one formula (typically Devine) consistently rather than comparing across formulas.
Yes. Formulas use gender-specific starting weights and multipliers. Female formulas start with lower base weights (45.5–53.1 kg vs 48–56.2 kg for males) and have similar or slightly lower per-inch multipliers depending on the formula. Gender selection affects all four calculations.
No. These formulas were developed for adults (typically ages 18-65). Children and adolescents have different growth patterns, body compositions, and healthy weight trajectories. Use CDC growth charts or pediatric-specific tools for youth weight assessment.
The comparison box shows the mathematical difference between your current weight and the average ideal weight across all four formulas. A green box with a checkmark indicates you’re within 1 kg of the average. A red box shows you’re above average. A green box without checkmark shows you’re below average. This is numerical comparison only — not health advice.
Measure your wrist circumference. For men: over 19 cm = large frame, 16.5–19 cm = medium frame, under 16.5 cm = small frame. For women: over 18 cm = large frame, 14–18 cm = medium frame, under 14 cm = small frame. Add or subtract 10% from ideal weight formulas to adjust for frame size.
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