Giant Weight Calculator
Example: 175 cm, 75 kg scaled to 8 ft: 203 kg
How heavy would an 8 foot person be? Scale yourself up with Galileo's square-cube law: make every dimension 1.4 times larger and your weight grows 2.7 times, while your bones only get 2 times stronger. Enter your height, weight and a target height to see your giant weight, the bone stress that comes with it, and how the tallest people ever measured compare.
Calculation results updated
Weight from your height to your giant height
You, giant you, and Robert Wadlow
How many of today's you the giant weighs
Each 🧍 = one of you at your current weight (75 kg)
Your Weight as a Giant
Same body proportions: mass grows with the cube of the height ratio
Weight if BMI Stayed the Same
The figure ideal-weight charts give: mass grows with the square of height
Scale Factor
BMI at Giant Size
Extra Stress on Bones
Bone Thickness Needed
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How to use this calculator
- Choose metric or imperial units, then enter your own height and weight.
- Enter the giant height you want to become. 244 cm or 96 inches is 8 feet.
- Read your same-proportions weight first: this is what geometry gives if nothing about your shape changes.
- Compare it with the same-BMI figure, which is the number height-weight charts would print.
- Open the Height Ladder to see every height from 150 to 300 cm at once, with the record holders marked.
How We Calculate This
Let k be the target height divided by your current height. Same-proportions weight is m × k³, the square-cube law, because every linear dimension grows by k and volume by k³. Same-BMI weight is m × k², since BMI equals mass divided by height squared. BMI at giant size under the same proportions is BMI × k. Stress on a bone is load divided by cross-sectional area, which scales as k³ ÷ k² = k, so the relative bone stress equals k. To hold stress at today's value the cross-section would have to grow by k³, which means bone width growing by k^1.5 rather than k. Robert Wadlow's figures (272 cm, 199 kg at death, 222.71 kg at his heaviest) and Sultan Kösen's height (251 cm) are Guinness World Records measurements. Height in imperial mode is entered in inches and converted at 2.54 cm per inch; weight converts at 0.45359237 kg per pound.
Methodology last reviewed: September 2026. How SparkCalc works
Sources: J. B. S. Haldane: On Being the Right Size (1926) · Scientific American: 388 years ago Galileo worked out why human giants can't exist · Guinness World Records: Tallest man ever (Robert Wadlow) · Guinness World Records: Tallest man living (Sultan Kösen) · CDC: Adult BMI categories
Why real giants weigh less than the cube predicts
Scale the example adult to Robert Wadlow's 272 cm with the same proportions and the model gives about 282 kg. Wadlow weighed 199 kg when he was last measured, and 222.71 kg at his heaviest. The gap is not an error in the law; it is a sign that his body did not keep an average adult's proportions. Wadlow's growth came from an overactive pituitary gland, and people with that condition tend to grow long and comparatively narrow. Their limbs lengthen faster than their frame broadens, so mass grows more slowly than the cube. The constant-BMI model errs the other way. It would give Wadlow roughly 181 kg from the same starting point, a little under his measured weight. Real giants sit between the two curves, which is why the calculator draws both.
What the bone-stress figure is telling you
A bone fails when the stress on it, load divided by cross-section, passes a limit set by the material. If you are 1.39 times taller in every dimension, your weight is 2.7 times greater but your femur's cross-section is only 1.94 times larger, so every square centimetre of bone carries 39 percent more. Your safety margin shrinks by the same amount. To keep the margin you have today, the cross-section would need to grow as fast as the load, by the cube of the scale factor, which means bone width growing by k to the power 1.5. That is the observation Galileo drew in 1638 when he compared a small animal's bone with the same bone enlarged for a creature three times taller, and it is why large land animals have thick, columnar legs rather than scaled-up versions of small ones.
Where the tallest people on record sit on the ladder
Guinness World Records lists Robert Wadlow as the tallest person ever measured, at 2.72 m (8 ft 11.1 in) on 27 June 1940, with a weight of 199 kg at his death a few weeks later and 222.71 kg on his twenty-first birthday. The tallest living man, Sultan Kösen, measured 251 cm (8 ft 2.8 in) in 2011. Both rows are marked in the Height Ladder tab so you can compare the model's numbers with the two heights that have actually been reached.
How heavy would a 7, 8, 9 or 10 foot person be?
Both columns scale the same starting adult: 175 cm (5 ft 9 in) and 75 kg (165 lb), BMI 24.5. Same proportions multiplies weight by the cube of the height ratio; same BMI multiplies it by the square.
| Height | Same proportions | Same BMI | Bone stress |
|---|---|---|---|
| 7 ft (213 cm) | 136 kg (300 lb) | 112 kg (246 lb) | +22% |
| 8 ft (244 cm) | 203 kg (447 lb) | 146 kg (321 lb) | +39% |
| 9 ft (274 cm) | 289 kg (637 lb) | 184 kg (406 lb) | +57% |
| 10 ft (305 cm) | 396 kg (874 lb) | 228 kg (502 lb) | +74% |
Robert Wadlow, 272 cm (8 ft 11 in), weighed 199 kg (439 lb) in 1940: lighter than proportional scaling predicts and heavier than a constant BMI would give.
Key terms
- Square-cube law
- When a shape is scaled by a factor k, its areas grow by k² and its volume by k³. Mass follows volume, so it grows faster than any strength that depends on cross-section.
- Scale factor (k)
- The target height divided by your current height. Every calculation on this page is a power of k.
- Bone stress
- Load divided by cross-sectional area. Under proportional scaling it grows in step with k, which is why a giant's skeleton would be under more strain than yours.
- Constant-BMI scaling
- Growing weight with the square of height so that BMI stays fixed. It is the assumption behind height-weight charts, not a physical law.
Frequently Asked Questions
How heavy would an 8 foot person be?
It depends on the build you scale up. A 175 cm (5 ft 9 in), 75 kg (165 lb) adult enlarged to 8 ft with the same proportions would weigh about 203 kg (447 lb), because mass grows with the cube of the height ratio. Keeping the same BMI instead gives about 146 kg (321 lb). Robert Wadlow, the tallest person ever measured at 2.72 m (8 ft 11.1 in), weighed 199 kg (439 lb), so real giants land between the two models.
Why does weight grow faster than height?
Volume is three-dimensional. If every measurement of a body is multiplied by k, its volume, and with it its mass, is multiplied by k × k × k. Double a person's height in proportion and they weigh eight times as much. This is the square-cube law that Galileo described in 1638.
Why could a giant not just walk around like a bigger person?
Bone strength depends on cross-sectional area, which grows with the square of size, while the load it carries grows with the cube. At twice the height the same-shaped bone carries twice the stress. Haldane's essay On Being the Right Size makes the point with a giant ten times human height: a thousand times the weight on bones ten times weaker for their load, so they would break their thighs at every step. Large animals cope by having disproportionately thick legs.
Which model do ideal-weight charts use?
Ideal-weight and BMI tables assume weight grows with the square of height, because that is what a constant BMI means. That works across the ordinary range of adult heights but understates the mass of a body that keeps its proportions. The calculator shows both so you can see the gap.
Is this a health or ideal-weight tool?
No. It is a physics scaling model that treats your body as a shape being enlarged or shrunk. It says nothing about what a healthy weight is for any real person, and the BMI it prints at giant size is a consequence of geometry, not a medical assessment.
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This is an educational physics model of geometric scaling. It is not a health, nutrition, or ideal-weight tool, and the BMI figures it prints describe a scaled shape, not a person. Real bodies do not scale in proportion, and the tallest people on record grew through medical conditions that changed their proportions.