Your two legs together account for roughly a third of your total body weight. For someone weighing around 70 kg (about 154 pounds), that puts both legs in the neighborhood of 23 kg, or just over 50 pounds combined. That figure comes from decades of anthropometric research breaking the human body into segments, and it holds reasonably well across a range of body sizes. But “a third” is just the starting point. What those legs are made of, how their composition differs between men and women, and the surprising ways leg mass shifts throughout a single day all make the picture more interesting than a simple percentage suggests.
What Your Legs Are Actually Made Of
When researchers want to know what is inside a limb, dual-energy X-ray absorptiometry (DEXA) scanning is one of the standard tools. It separates tissue into three compartments: lean mass (mostly muscle), fat, and bone mineral. In a study using DEXA to assess regional body composition, average leg muscle mass came out to about 11.4 kg for women and 17.4 kg for men.1PubMed. Assessment of the composition of major body regions by dual-energy X-ray absorptiometry (DEXA), with special reference to limb muscle mass Those numbers represent just the muscle portion; once you add fat, bone, skin, connective tissue, and blood, the total climbs to that familiar one-third-of-body-weight range.
Bone mineral contributes a relatively small slice. In both men and women, regional bone proportions in the legs fell in the range of roughly 3 to 6 percent of the leg’s total mass.1PubMed. Assessment of the composition of major body regions by dual-energy X-ray absorptiometry (DEXA), with special reference to limb muscle mass That might seem surprisingly low, but bones are dense yet slender compared with the thick sheaths of muscle and adipose tissue surrounding them. Fat, on the other hand, can make up anywhere from about a sixth to nearly a third of a leg’s weight depending on the individual, which brings us to the differences between the sexes.
How Leg Composition Differs Between Men and Women
Men and women carry their weight in visibly different places, and the legs are where some of the starkest contrasts show up. In the DEXA study mentioned above, the proportion of fat in each body region was consistently higher in women than in men, with women’s legs containing roughly 20 to 31 percent fat compared with 16 to 18 percent in men. Women also stored a larger share of their total body fat in the legs: about 49 percent of body fat lived in the legs for women, versus around 38 percent for men.1PubMed. Assessment of the composition of major body regions by dual-energy X-ray absorptiometry (DEXA), with special reference to limb muscle mass Men, meanwhile, packed proportionally more fat into the trunk.
These patterns are not just an adult phenomenon. Research tracking fat distribution from childhood through young adulthood has shown that girls already have less waist fat and more hip and extremity fat than boys even before puberty. The gap widens dramatically during and after puberty: by early adulthood, women had about 48 percent less waist fat (adjusted for hip fat) than men, while carrying considerably more fat in the hips and limbs at every pubertal stage studied.2PubMed. Sex differences in regional body fat distribution from pre- to postpuberty This means the sex-linked pattern of heavier, fattier legs relative to the trunk in women is not purely a consequence of adult hormones; it begins earlier and then hormones amplify it.
In practical terms, two people of identical total body weight can have meaningfully different leg weights simply because of these distribution patterns. A woman’s legs may carry more fat mass while a man’s carry more muscle mass, and the totals can end up roughly similar in absolute terms while differing sharply in composition.
Aging and the Quiet Loss of Leg Muscle
One of the less visible changes with aging is that leg mass gradually shifts in composition even when the number on the bathroom scale stays the same. A longitudinal study of healthy, independently living older adults found that over a roughly two-year follow-up period, men lost an average of about 0.7 kg of leg skeletal muscle, and women lost about 0.3 kg, despite maintaining stable total body weight.3PubMed. Weight stability masks sarcopenia in elderly men and women The muscle that disappeared was being replaced by fat and other tissue, making the loss invisible on a scale but very real in terms of strength and function.
This process, sarcopenia, is particularly concentrated in the legs. The same study showed that nearly all of the appendicular muscle loss came from the legs rather than the arms, and the rate of leg muscle loss was greater in men.3PubMed. Weight stability masks sarcopenia in elderly men and women Because leg muscles are responsible for standing, walking, and climbing stairs, this hidden trade of muscle for fat has outsized consequences for mobility and fall risk. Your legs might weigh the same at 75 as they did at 65, but they may contain significantly less of the tissue that keeps you upright.
How Training Reshapes Leg Mass
If aging pulls muscle mass out of the legs, athletic training can push it in, though not in a uniform way. A study comparing elite sprinters to non-sprinters using MRI found that sprinters had about 22 percent more limb muscle per unit of body size overall, but the extra muscle was not distributed evenly. The muscles crossing the hip and knee joints were about 30 percent larger on average, with some individual muscles up to 54 percent larger.4PubMed. Adding muscle where you need it: non-uniform hypertrophy patterns in elite sprinters Muscles around the ankle, by contrast, were mostly not significantly different from those of non-sprinters, with one exception (a deep calf muscle called the tibialis posterior).
This non-uniform pattern makes biomechanical sense. The hip and knee extensors and flexors are the primary drivers of the explosive force needed to accelerate in a sprint, so years of sprint training selectively enlarges them. For the general reader, the takeaway is that “leg weight” is not a fixed property. Someone who runs, cycles, or does heavy squatting may carry several extra kilograms of muscle in their legs compared with a sedentary person of the same total body weight. Two people at 80 kg can have very different leg masses depending on how they use those legs.
Your Legs Gain and Lose Weight Throughout the Day
Here is something most people never consider: your legs are heavier at the end of the day than at the beginning. The culprit is gravity-driven fluid pooling. When you stand or sit upright, blood and interstitial fluid accumulate in the lower limbs. Research measuring calf volume changes during venous occlusion found that most of the volume change came from filling of deep venous spaces, with deep veins accounting for over 90 percent of the volume shift at moderate pressures and about half even at higher pressures.5ScienceDirect (The American Journal of Cardiology). Deep venous contribution to hydrostatic blood volume change in the human leg Throughout a long day on your feet, this pooling can add a noticeable amount of fluid volume to your legs, which is part of why shoes feel tighter in the evening and why rings can be harder to pull off after a day of standing.
The reverse happens when gravity is removed. When astronauts enter microgravity, blood volume shifts rapidly from the legs to the upper body, creating the puffy face and “chicken legs” that crew members commonly report in the first days of spaceflight.6PubMed. Body fluid regulation in micro-gravity differs from that on Earth: an overview You might expect this headward shift to trigger the kidneys to dump the extra fluid, but research has shown that the expected diuresis largely does not happen: the acute shift of blood volume from the legs to the upper body in microgravity has not resulted in the negative water and sodium balances that classic physiology would predict.7PubMed. Water and sodium balances and their relation to body mass changes in microgravity The body holds onto that fluid, and researchers are still working out why. For earthbound purposes, the point is that several hundred milliliters of fluid can shuttle in and out of your legs depending on your posture, making leg weight genuinely variable hour to hour.
When Leg Size Becomes a Medical Issue
There is a condition called lipedema in which the legs accumulate disproportionate amounts of fat that does not respond to diet or exercise. Women with lipedema can have legs that weigh dramatically more than expected for their body size, with the added fat concentrated from the hips to the ankles, often sparing the feet entirely. This creates a distinctive appearance and causes progressive pain, heaviness, and difficulty moving.
Research on lipedema reduction surgery in 66 women showed significant improvements not only in segmental body fat mass but also in mobility measures including gait velocity, ability to rise from a chair, and stair climbing.8PubMed Central. Lipedema Reduction Surgery Improves Pain, Mobility, Physical Function, and Quality of Life: Case Series Report The sheer extra weight in the legs had been a functional burden, and reducing it translated directly into better physical performance and quality of life.
Lipedema also interacts with the age-related muscle loss discussed earlier in a particularly unpleasant way. A cross-sectional study of women with lower-extremity lipedema found that advancing disease stage correlated with reduced muscle thickness, weaker grip strength, slower gait, and worse performance on a sit-to-stand test, with stage 3 patients showing the highest rates of sarcopenia.9PubMed. Prevalence of sarcopenia and its functional correlates in women with lower-extremity lipedema: A cross-sectional observational study In other words, the legs get heavier from excess fat while simultaneously losing muscle, compounding the mobility burden. This is a stark illustration of why the composition of leg weight matters at least as much as the total number.
Estimating Body Weight After Limb Loss
Knowledge of how much each body segment weighs becomes clinically important when someone has had a limb amputated. Clinicians need to estimate what a patient’s body weight would have been with the missing limb to make accurate nutritional assessments, calculate drug dosages, and set rehabilitation targets. Standard anthropometric reference tables assign approximate percentages to each segment: a foot might represent about 1.5 percent of body weight, a below-knee segment around 6 percent, and the entire leg roughly 16 percent.
Research on estimating body weight in people with lower-limb amputations has explored how well these corrected estimates work in practice. One study comparing estimated whole-body BMI to observed BMI in amputees found that the estimated version actually tracked better with independent measures of nutritional status, like upper arm circumference, and performed comparably to BMI calculated in non-amputee controls.10PubMed Central. Method for estimating body weight in persons with lower-limb amputation and its implication for their nutritional assessment The segment percentages, rough as they are, turn out to be useful enough for clinical decision-making.
Prosthetic design also grapples with questions of leg mass, though in a more counterintuitive direction. Modern prosthetic limbs are typically much lighter than the biological limbs they replace, and you might assume that lighter is always better. A systematic review of theoretical models and experimental studies on prosthetic inertial loading reached a more nuanced conclusion: the predictions suggest that the inertial loading of current lightweight prostheses does not need to be decreased and sometimes may need to be increased to improve walking patterns.11Archives of Physical Medicine and Rehabilitation. Inertial Loading of Lower-Limb Prostheses: A Systematic Review of Theoretical Models and Experimental Studies A leg that is too light can feel unnatural and actually disrupt gait. The brain expects a certain amount of pendular weight to be swinging beneath the hip, and matching that expectation matters for fluid walking.
Leg Mass in Other Animals
Humans are not the only species for whom leg mass distribution matters. In fact, some of the most elegant examples of leg-mass engineering come from the animal kingdom, and they highlight why where the mass sits can be more important than how much there is.
The ostrich, the fastest-running bird on the planet, is a case study in this principle. Research on ostrich locomotor anatomy found that the bird’s leg muscle mass is concentrated far more toward the hip joint than in its closest relatives. Its distal leg elements, the long lower segments equivalent to our shins and feet, are the relatively longest and lightest among the ratite family.12HeiDOK. Structural attributes contributing to locomotor performance in the ostrich This is an optimization based on pendulum physics: concentrating mass near the pivot point while keeping the swinging end light allows the limb to swing faster with less energy. It is the same reason figure skaters pull their arms in to spin faster.
Human sprinters show a milder version of the same pattern. Recall that elite sprinters had their largest hypertrophy in the hip and knee muscles, not around the ankle.4PubMed. Adding muscle where you need it: non-uniform hypertrophy patterns in elite sprinters Heavy calves would slow limb turnover; powerful glutes and quads closer to the hip provide force without adding mass to the swinging end of the limb. Evolution and training independently arrived at the same engineering solution: for speed, put the weight where the pivot is, not where the pendulum swings.
This principle extends to distance runners and endurance athletes as well, who tend to have notably lighter lower legs than sprinters or power athletes. Marathon runners often have slender calves not because they lack fitness but because lighter distal limbs reduce the metabolic cost of swinging each leg forward thousands of times per mile. The body is remarkably responsive to the demands placed on it, building mass where it serves the task and keeping it off where it would be a liability.