Adjusted Body Weight Calculator
Amputee-adjusted weight using percent of limb loss
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Need a fast answer on amputee-adjusted weight using percent of limb loss? Adjusted Body Weight Calculator answers with the steps beside it. You supply Measured Weight (kg) and Amputation (% of body weight) to Adjusted Body Weight; the answer follows at once. Adjusted Body Weight displays each intermediate figure as well. Adjusted Body Weight suits budgeting and planning checks. No sign-up is needed for Adjusted Body Weight. The math runs on your device. Adjusted Body Weight sits in the Health section next to related tools and adjusted body weight calculator amputee limb loss percentage. Adjusted Body Weight is designed for real people. Labels stay plain. Adjusted Body Weight stays bookmarked for next time.
What the defaults give
A measured weight of 80 kg with a 6% amputation works back to 85.1 kg — the estimated body weight before the limb was lost.
The scale cannot weigh what is no longer there. Amputee-adjusted weight restores that missing mass so BMI, calorie needs and weight-based dosing are calculated on the whole body rather than the remainder.
The formula
Adjusted weight = measured weight ÷ (1 − amputation fraction).
With 6% loss: 1 − 0.06 = 0.94, and 80 ÷ 0.94 = 85.1 kg. The measured figure is divided, not multiplied, because the 80 kg represents only 94% of the original body.
Worked example
Measured 80 kg
Amputation 6% of body weight
1 − 0.06 = 0.94
80 ÷ 0.94 = 85.1 kg adjusted
Using the raw 80 kg instead would understate the pre-amputation weight by 5.1 kg, which moves a BMI at 1.75 m from 26.1 to 27.8 — enough to shift a category boundary.
Percentage by level of amputation
- Below knee — roughly 5–6% of body weight.
- Above knee — roughly 11–16%, because more muscle is removed.
- Below elbow — about 2%.
- Above elbow — about 5%.
- Whole arm — about 6–7%; whole leg, 16–18%.
Where the adjusted weight belongs
Use it for BMI, basal metabolic rate and any drug dose based on body weight or body surface area. Do not use it for fluid resuscitation, nutritional requirements during acute illness, or anything that depends on current lean mass — those are measured on the body that exists now.
Limits of the estimate
The percentages are population averages. Body composition, the exact level of the amputation and the proportion of muscle lost all change the true figure, and a clinician who knows the patient’s history should be the one to settle it.
Frequently Asked Questions
Why does the adjusted weight come out higher than the measured weight?
Because the measured 80 kg is only 94% of the original body after a 6% loss. Dividing by 0.94 restores the missing mass, giving 85.1 kg.
What percentage should I enter for an above-knee amputation?
Roughly 11–16% of body weight, depending on how much of the femur is retained. Below-knee amputations are closer to 5–6%.
Should BMI use the adjusted weight?
Yes. BMI built on the measured weight overstates adiposity, because it treats the missing limb as lost tissue rather than lost mass. The adjusted figure keeps the ratio meaningful.
Is the adjusted weight used for drug dosing?
For weight-based doses of many drugs, yes — but not universally. Some drugs are dosed on ideal or lean body weight instead, and the choice is a clinical decision.
How accurate is it?
It is an estimate from population averages. The level of amputation and the individual’s build both matter, so treat the result as a better starting point than the raw scale reading, not as a measurement.
What percentage is a below-elbow amputation?
About 2% of body weight, so an 80 kg measured weight adjusts to 80 ÷ 0.98 = 81.6 kg. Above-elbow is roughly 5%, and a whole arm 6–7% — the further up the limb, the more the estimate moves.
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