Ideal Weight Calculator

Consensus Ideal Weight

Formulas {{ formatBandSelected(formulaMinSelected, formulaMaxSelected) }} Healthy BMI {{ formatBandSelected(healthyMinSelected, healthyMaxSelected) }} Target BMI {{ safeTargetBmi.toFixed(1) }} = {{ formatWeightWithUnit(targetWeightSelected) }} Spread {{ formatWeightWithUnit(formulaSpreadSelected) }} {{ currentStatusBadge }}

Formula profile:

Accepted values: male coefficients or female coefficients; choose the set your reference names.

Height:

Examples: 172 cm, 68 in, or 5 ft 8 in; switching units converts the same height.

Result unit:

Choose kg or lb; an entered current weight converts when you switch units.

Target BMI:

Enter 18.5 to 24.9; default 22.0 gives a midpoint-style BMI target.

BMI

Current weight:

Enter current weight in the selected result unit, or leave blank to hide comparison.

Frame size:

Options: Small -10%, Medium no shift, Large +10%; the next mode controls where it applies.

Frame adjustment mode:

Choose Hamwi only for the classic adjustment; use all formulas only to match legacy output.

Under-5 ft handling:

Subtract mode lowers formulas below 5 ft; clamp mode holds each formula at its base constant.

Area	Badge	Readout	Detail	Copy
{{ card.title }}	{{ card.badge }}	{{ card.headline }}	{{ card.detail }}

Formula	{{ weightUnit.toUpperCase() }}	kg	lb	Vs consensus	Current gap	How to read it	Copy
{{ row.name }} {{ row.shortNote }}	{{ formatWeight(row.selected) }}	{{ formatWeight(row.kg) }}	{{ formatWeight(row.lb) }}	{{ row.deltaFromConsensusText }}	{{ row.deltaFromCurrentText }}	{{ row.guidance }}

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Ideal body weight is a height-based reference, not a single universal "correct" weight for every adult. The idea came from older height-weight tables and later equation sets, so the answer changes a little depending on whether you use Devine, Hamwi, Robinson, or Miller. That is why one person can enter one height and still get several reasonable reference values instead of one final truth.

This calculator makes those differences easy to read. You choose the male or female coefficient profile, enter height in centimetres, inches, or feet plus inches, and the tool returns each formula result, a consensus average, the full formula band, an adult healthy-BMI corridor for the same height, and a target-weight line based on the BMI you choose inside that corridor. Add current weight and the result also shows whether your present value sits below, inside, or above the visible bands.

The split between formula band and BMI corridor is the most useful part of the tool. The formula band answers, "Where do these classic ideal-weight equations cluster for this height?" The BMI corridor answers, "What weight span corresponds to an adult BMI of 18.5 to 24.9 at this height?" Those are related questions, but they are not identical, and the calculator keeps them separate on purpose.

Use the result as planning context, not diagnosis. The tool is built for adult height-based reference checks, so it does not account for pregnancy, edema, pediatric growth patterns, body-fat distribution, or unusually muscular builds. The calculation runs in the browser, but the page also mirrors changed inputs into the URL so a copied link can reopen the same state. That is convenient for repeat checks and less convenient if you do not want measurements embedded in a shared link.

Technical Details

The calculator uses four classic equations. Each one starts from a base weight for 5 feet exactly, then adds or subtracts a fixed amount for every inch above or below that anchor. The adult healthy-BMI corridor is computed differently: it converts BMI 18.5 and BMI 24.9 into weight at the entered height. The target BMI field does the same thing for one chosen BMI inside that corridor, with a default of 22.0.

\begin{array}{lcl} h_{ex} & = & \frac{h_{cm} - 152.4}{2.54} \\ W_{formula} & = & b + s * h_{ex} \\ W_{BMI-low} & = & 18.5 * h^{2} \\ W_{BMI-high} & = & 24.9 * h^{2} \\ W_{target} & = & {BMI}_{target} * h^{2} \end{array}

Here, h is height in meters for the BMI formulas, h_ex is the number of inches relative to the 5-foot anchor, b is the formula base constant, and s is the per-inch step size. In the recommended under-5-foot mode, heights below 5 feet produce negative extra inches and therefore lower results. In clamp mode, extra inches stop at zero, so the formulas stay at their base constants instead.

Classic ideal weight equations used by the calculator
Formula	Male coefficients (kg)	Female coefficients (kg)	How the tool frames it
Devine	`50 + 2.3 * h_ex`	`45.5 + 2.3 * h_ex`	Often used when a dosing or clinical reference names Devine directly.
Hamwi	`48 + 2.7 * h_ex`	`45.5 + 2.2 * h_ex`	The default frame-size adjustment applies here, matching the tool's recommended mode.
Robinson	`52 + 1.9 * h_ex`	`49 + 1.7 * h_ex`	Usually lands a little tighter than Hamwi for the same height.
Miller	`56.2 + 1.41 * h_ex`	`53.1 + 1.36 * h_ex`	Starts from a higher base and often marks the upper end of the cluster.

Advanced controls and how they change the result
Control	What changes	What to expect
Frame size	Applies a 10% decrease for small or 10% increase for large.	In the recommended mode, only Hamwi shifts. In legacy mode, all four formulas shift together.
Frame adjustment mode	Chooses whether frame size affects Hamwi only or every formula.	Use Hamwi only when you want the narrower historical-style adjustment. Use all formulas only when you need that broader legacy behavior.
Under-5-foot handling	Either keeps subtracting below 5 feet or clamps all formulas at their base constants.	Subtract mode usually feels more continuous. Clamp mode preserves the older fixed-base behavior for shorter heights.
Target BMI	Translates one BMI inside 18.5 to 24.9 into a single target weight.	This does not change the formula outputs. It only adds a separate reference point inside the BMI corridor.

The summary box labels the consensus ideal weight as the arithmetic mean of the four formula rows. The formula band is the minimum-to-maximum span across those same rows. The healthy corridor is independent of the formula cluster, because it comes from BMI math alone. Depending on height and settings, the two bands can overlap almost completely, overlap only partly, or sit noticeably apart.

The tool also includes practical guardrails. If you enter a height outside the common adult range used by the caution text, the result stays available but is framed as a rough estimate. That is consistent with how ideal-weight equations are usually used: as quick reference weights for adult planning, medication or ventilation contexts, and comparison work, not as a complete statement about body composition or health.

Everyday Use & Decision Guide

The fastest first pass is simple. Pick the coefficient profile you need, enter height, leave the advanced section at its defaults, and read the summary badges before opening the tabs. That immediately tells you the consensus ideal weight, the formula range, the healthy BMI corridor, and the target BMI weight for the same height.

Use the result that matches the question you are trying to answer. If a clinician, article, ventilation workflow, or dosing rule names one formula, go straight to that row in Formula Comparison. If you only need a quick midpoint across the classic equations, the consensus figure is the better anchor. If the question is really about adult screening range at a given height, the healthy BMI corridor is more relevant than any one ideal-weight equation.

The optional current-weight field turns the calculator from a pure reference tool into a planning tool. Once you enter current weight, the summary line tells you whether that value is inside both visible bands, inside only one of them, or outside both. That distinction is useful because someone can be comfortably inside the healthy BMI corridor while still sitting above the tighter classic-formula cluster, or the reverse.

The tabs are arranged by job. Planning Summary condenses the main story into four cards. Formula Comparison is the best place to compare the named methods and export the table as copied CSV, downloaded CSV, or DOCX. Formula Weights turns the four rows into a bar chart with the BMI corridor and reference lines layered on top. Weight Corridor strips the view down to band overlap and midpoint markers. JSON exposes the full structured state for copying or download.

Open the advanced controls only when you have a reason. Frame settings are useful when you want a Hamwi-style small or large build adjustment. The under-5-foot mode matters only for shorter heights. The target BMI field is helpful when you want one specific anchor inside the healthy corridor, but it does not change the formula rows themselves.

Step-by-Step Guide

Choose the male or female coefficient profile that matches the equation reference you need to reproduce.
Enter height in centimetres, inches, or feet plus inches. The calculator keeps the physical height aligned when you switch formats, so use whichever entry style is least error-prone for you.
Read the summary box first. It shows the consensus ideal weight, formula span, healthy BMI corridor, and target BMI weight without forcing you into a chart immediately.
Add current weight if you want status against both reference bands. Leave it blank if you only need the height-based outputs.
Open Formula Comparison for named rows and table exports. Use Formula Weights when you want to see which formula is lowest or highest at a glance.
Use advanced settings last, not first. Start with medium frame, Hamwi-only frame mode, subtract-below-5-foot handling, and the default target BMI unless your workflow needs something else.

Interpreting Results

How to interpret each major result field
Result field	What it means	How to use it
Consensus ideal weight	The average of Devine, Hamwi, Robinson, and Miller for the current settings.	Use it as a quick midpoint when no single formula has priority.
Formula band	The minimum-to-maximum span across the four formula rows.	A narrow span means the formulas largely agree. A wider span means method choice matters more.
Healthy BMI corridor	The adult BMI 18.5 to 24.9 weight range at the entered height.	Use it when you want an adult screening range rather than a named ideal-weight equation.
Target BMI weight	One weight produced by the chosen BMI target inside the corridor.	Useful for planning around one anchor value instead of the full BMI span.
Current status badge	A comparison of current weight against both the formula band and the BMI corridor.	Read it together with the gap text so you know whether the difference is small, large, formula-only, or BMI-only.
Overlap summary	The shared part of the formula band and BMI corridor, or the gap between them when they do not overlap.	Helpful when you want to see whether the classic equations sit inside the adult BMI corridor or drift away from it.

The spread badge is the quickest warning that formula choice may matter. When the four rows cluster tightly, the midpoint is usually enough for a broad planning conversation. When the spread widens, it becomes more important to check whether a protocol wants Devine, whether you deliberately changed Hamwi with a frame adjustment, or whether shorter-height handling is driving the gap.

A current weight that sits inside the healthy BMI corridor but outside the formula band does not mean one side is wrong. It means the broader BMI-based screening range and the tighter classic-formula cluster are telling slightly different stories. The tool surfaces that difference instead of hiding it behind one headline number.

If the result looks implausible, check units before anything else. A wrong height unit will distort every formula, every BMI-based output, every chart, and every export. Changing the display unit between kilograms and pounds should only rescale the same physical result.

Worked Examples

Example 1: default adult reference check. With male coefficients, height 172 cm, medium frame, Hamwi-only frame mode, and target BMI 22.0, the four formulas come out to 67.7 kg, 68.8 kg, 66.7 kg, and 67.1 kg. The consensus ideal weight is 67.6 kg, the formula band is 66.7 to 68.8 kg, and the healthy BMI corridor at the same height is much wider at 54.7 to 73.7 kg. The target BMI weight is 65.1 kg. This is the classic pattern where the formula cluster sits comfortably inside the broader adult BMI range.

Example 2: current weight inside BMI range but above the formula cluster. With female coefficients, height 165 cm, small frame, Hamwi-only frame mode, target BMI 21.5, and current weight 62.0 kg, the formula rows are 56.9 kg, 50.8 kg, 57.4 kg, and 59.9 kg. The consensus is 56.2 kg and the formula band is 50.8 to 59.9 kg. The healthy BMI corridor is 50.4 to 67.8 kg, so 62.0 kg sits above the classic-formula cluster but still inside the healthy BMI corridor. That is exactly the kind of mixed reading the tool is built to show clearly.

Example 3: shorter height with different under-5-foot rules. With male coefficients at 150 cm, the recommended subtract mode gives 47.8 kg, 45.5 kg, 50.2 kg, and 54.9 kg, with a consensus of 49.6 kg. If you switch to clamp mode, the same height becomes 50.0 kg, 48.0 kg, 52.0 kg, and 56.2 kg, with a consensus of 51.6 kg. The healthy BMI corridor stays the same in both cases at 41.6 to 56.0 kg because BMI math does not use the under-5-foot formula rule. Only the classic ideal-weight rows change.

FAQ:

Why does the calculator show four ideal weights instead of one?

Because Devine, Hamwi, Robinson, and Miller are separate published equation families. They share the same basic idea but use different constants and slopes, so the calculator keeps the rows separate and also shows their average.

Is the consensus number the medically correct answer?

No. The consensus value is just the arithmetic mean of the four displayed formulas. It is useful as a midpoint, not as proof that the average is somehow more "true" than a named formula required by a protocol.

Why can the formula band and the healthy BMI corridor disagree?

They come from different math. The formula band comes from older height-based ideal-weight equations, while the healthy corridor comes from adult BMI cutoffs applied to the same height. Agreement is common, but it is not guaranteed.

What does frame size actually do here?

It applies a 10% downshift for small or 10% upshift for large. In the recommended mode, only Hamwi changes. In legacy mode, all four formulas shift together. It is a rough sensitivity setting, not a direct measure of skeletal frame or body composition.

Does the calculation stay on my device?

The calculation itself runs in the browser and the exports are generated from that local state. The important caveat is that changed inputs are mirrored into the page URL, so sharing the link can also share the entered measurements.

Should children, teens, or pregnancy planning use this result directly?

No. Adult BMI cutoffs and adult ideal-weight equations are not a substitute for pediatric growth-chart interpretation or pregnancy-specific guidance. Use this tool only as an adult reference unless a clinician tells you otherwise.

Glossary:

Ideal body weight: A height-based reference weight estimated from a published rule or equation, often used for adult planning or specific clinical calculations.
Consensus ideal weight: The tool's average across Devine, Hamwi, Robinson, and Miller for the current settings.
Formula band: The full range from the lowest to the highest formula result.
Healthy BMI corridor: The adult weight span at the entered height that corresponds to BMI 18.5 through 24.9.
Target BMI weight: The single weight produced when one chosen BMI inside the healthy corridor is converted back to body weight at the entered height.
Clamp mode: The short-height option that stops extra inches at zero so the classic equations stay at their 5-foot base constants for shorter heights.

References:

The origin of the "ideal" body weight equations, Annals of Pharmacotherapy, 2000.
Ideal body weight: A commentary, Journal of Perioperative Practice, 2021.
Adult BMI Categories, Centers for Disease Control and Prevention, March 19, 2024.
BMI Frequently Asked Questions, Centers for Disease Control and Prevention, June 28, 2024.