A few weeks ago we wrote about the idea of "reverse BMI" — solving the BMI formula backward, for weight instead of BMI. Back then it was a hand-calculation exercise. It isn't anymore: a live Reverse BMI quick field has now shipped directly on the BMI Calculator page, in both US and metric units. Here's exactly what it does and how to use it.
What actually shipped
Quick answerThe BMI Calculator now includes a Reverse BMI quick field — labeled "what should I weigh for a target BMI?" — sitting right under the main height/weight inputs. Type a target BMI, and it shows the matching weight for your entered height instantly, without pressing the main Calculate button.
This is a small, focused addition rather than a redesign. The core calculator — height, weight, Calculate button, gauge, category, healthy weight range — works exactly as it did before. The new field is a second, independent input sitting alongside it, built specifically for the "what weight gets me to a specific BMI" question rather than the "what's my BMI right now" question.
Under the hood it's the same trusted formula rearranged: weight = target BMI × height² ÷ 703 (in US units). Nothing about the underlying math changed — what changed is that you no longer have to do that rearrangement yourself.
Where to find it and how to use it
Quick answerOn the US units panel, the field appears directly below the height/weight row and the height-in-inches preset chips, labeled "Reverse BMI: what should I weigh for a target BMI?" with a Target BMI input defaulting to 22 and an output box that updates as you type.
To try it: open the BMI Calculator, make sure the "US units (lb, ft/in)" tab is selected, and look just below the height and weight fields. There's a thin divider line, then the Reverse BMI section. Enter your height in the main fields above (say, 5'9"), then change the Target BMI field from its default of 22 to whatever value you want — 24.9 for the top of the normal range, or 20 for something more conservative. The output box updates with the matching weight in pounds.
For example, at a height of 5'9" (69 inches), a target BMI of 22 works out to roughly 149 lb — the same figure you'd get running the reverse formula by hand, just without doing the multiplication and division yourself.
Note: the field reads the height you've already entered in the main calculator, so there's no need to re-type your height a second time — only the target BMI is a separate input.
It works in metric too
Quick answerSwitching to the "Metric (kg, cm)" tab shows a matching Reverse BMI field using your height in centimeters, with the same default Target BMI of 22 and its own output box.
The calculator's unit toggle at the top switches the entire panel — height/weight inputs, hints, and now the Reverse BMI section too. So if you'd rather think in centimeters and kilograms, the target-BMI-to-weight conversion is available there as well, using the metric form of the same underlying relationship (BMI = kg ÷ m²) solved for weight instead.
As an illustrative example: at a height of 175 cm, a target BMI of 22 corresponds to a weight of roughly 67.4 kg (22 × 1.75² ≈ 67.4). The exact figure the field shows will match whatever height is currently entered in the metric panel.
Why a live field beats doing the math by hand
Quick answerThe formula was never complicated, but a live field removes friction: no calculator app, no risk of a squaring or division slip, and it's easy to try several target BMI values in a row to see how the matching weight shifts.
The reverse-BMI arithmetic — squaring a height, multiplying by a target BMI, dividing by 703 — is only a few keystrokes, but it's exactly the kind of small friction that stops people from actually running the numbers. A live field turns "let me get out a calculator" into "let me just type a different number and watch the output change," which makes it much easier to compare a few candidate targets side by side — for instance, checking what 20, 22, and 24 all translate to for the same height before settling on one.
It also keeps the reverse calculation visually next to the forward one, which is a useful reminder that they're the same relationship viewed from two directions: one field answers "what's my BMI at my current weight," the other answers "what weight gets me a specific BMI." Having both on one page makes it easy to move between diagnosing where you are and planning where you'd like to be.
Frequently asked questions
Where exactly is the new Reverse BMI field on the calculator?
It sits directly beneath the height/weight inputs, inside both the US units and Metric panels of the BMI Calculator, labeled "Reverse BMI: what should I weigh for a target BMI?". It appears in whichever unit mode you have selected, so switching from US to Metric shows a matching field using centimeters and kilograms instead of feet, inches, and pounds.
Does the new field replace the main BMI calculation?
No — the Reverse BMI field is an addition next to the existing calculator, not a replacement. The main Calculate button still works exactly as before, taking your current height and weight to produce your BMI, category, and healthy weight range. The new field answers a separate question: given a target BMI, what weight would produce it.
Does the Reverse BMI field require pressing the Calculate button?
No. The Reverse BMI field is a standalone quick field that reads your height and target BMI directly and shows the matching weight in its own output box, separate from the main result card that appears after pressing Calculate. You can use one, the other, or both without needing to submit the form twice.
What number does the Reverse BMI field actually output?
It outputs a single weight figure — in pounds when the US units panel is active, in kilograms when the Metric panel is active — representing the weight that would produce your entered target BMI at your entered height. It does not output a category label or a range, just the matching weight number.
Is the new field available in both the US and metric unit modes?
Yes. The calculator's segmented control lets you switch between US units (lb, ft/in) and Metric (kg, cm), and the Reverse BMI quick field is present in both panels with its own target-BMI input and output box, so the feature works the same way regardless of which unit system you prefer.