How big are 20 inch thighs?
It depends if you know how to measure your thighs correctly.
For example, if you're measuring your legs close to your knee, then a reading of 20 inches is a bit bigger than normal.
However, if you measure around your mid or upper thigh, which is the correct way to measure your legs, then 20 inch thighs are actually smaller than average. And that's for both men and women.
Learn How Your Thighs Compare:
- 14 inch legs
- 17 inch legs
- 18 inch legs
- 19 inch legs
- 21 inch legs
- 22 inch legs
- 23 inch legs
- 24 inch legs
- 25 inch legs
Are 20 inch thighs big for females?
If you have 20 inch thighs as a woman, then your thighs are a full inch smaller than average. And that's when you factor in all ages (elderly women have considerably slimmer thighs due to age-related muscle loss).
When you just look at younger women (i.e., those who are most likely to be concerned about their thigh size in the first place), 20″ thighs are actually two inches smaller than average.
While it's true that 20 inch legs will look slimmer the taller that you are, 20 in thighs will still look pretty slim on just about every kind of female body.
The reason that an equivalent thigh size always looks a bit slimmer on a taller woman is that the same amount of thigh mass is stretched over a longer surface area. As such, the legs appear less bulky.
Similarly, if you have toned thighs, then your legs may also look slimmer due to having better muscle definition.
None of this is to say, of course, that your thighs are too big if they measure more than 20 inches. Some women, for example, have genetically muscular legs, whereas others tend to store a lot of their body fat on their legs.
How about for men?
In general, 20 inch thighs are a bit on the small side for men, especially for those who lift weights and spend plenty of time in the squat rack.
The one exception to this is short lifters who are very lean. If you're 5'5″ and a few days out from a bodybuilding contest, then 20 inch quads can actually look quite big if they have sharp striations and visible vascularity.
Of course, having 20 inch quads is more likely to be a sign that your legs are underdeveloped, at least from a bodybuilding perspective (it's possible to have 20 inch legs while still having a perfectly healthy BMI, for example). 
Additionally, the longer that your femurs are, the smaller that your 20 in thighs will look. This is simply because when your thigh bones are long, your muscle mass is spread over a longer surface area; thus, the quads look less bulky and have less of a sweep.
How can you develop your 20 inch quads?
Although the legs aren't generally a point of huge concern for men in the same way that they typically are for women, many men still wish that their legs were bigger.
And yet, so many guys perform half reps nowhere near failure and expect to get results.
If you wouldn't do a half rep bench press, don't do a half rep squat or leg press.
Performing a full range of motion puts your legs under greater levels of tension and thus gives your quads, glutes, and hamstrings a more potent hypertrophic stimulus.
Don't feel that you need to work your legs more than twice a week, either. Since they can handle a lot of training volume, big muscles like the quads and hams take a long time to recover, so you can often make excellent gains (and arguably even optimal gains) by just hitting them once per week.
On the nutrition side of things, make sure that in addition to eating enough healthy fats to promote optimal hormone production—and enough carbs to fuel your workouts—you're also eating enough protein to maximize your quad development.
Research shows that consuming 40g of protein after training rather than just 20g results in a greater elevation of muscle protein synthesis.  So make sure to put your efforts in the gym to good use by feeding your muscles with the protein that they crave.
Should you slim your 20 inch legs?
Unless your 20 inch thighs are indicative of you being overweight, there's no reason why you need to slim your thighs.
Of course, some people want to make their thighs look slimmer for aesthetic reasons.
But considering that some of the best quality data shows that 20 inch and 20.5 inch thighs are already smaller than average, there appears to be little reason for making your thighs smaller than they currently are.
Lifting leg weights, or even just doing bodyweight squats, can make your thighs look more toned without necessarily making them thinner. So depending on the look that you're aiming for, you might want to add resistance training into your exercise regime.
Conclusion: Is it okay to have a 20 inch thigh circumference?
Yes! It's perfectly okay to have a 20 inch thigh circumference in the vast majority of cases!
The only (rare) exception is when your thigh size is indicative of you being underweight or overweight.
As we established, all of the data points to 20 inch thighs being smaller than average for men and women. But even if your thighs are bigger than this, you shouldn't worry unless the size of your legs is a sign of other health problems.
- What Is My BMI? (2022, January 21). Centers for Disease Control and Prevention. https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html
- Macnaughton, L. S., Wardle, S. L., Witard, O. C., McGlory, C., Hamilton, D. L., Jeromson, S., Lawrence, C. E., Wallis, G. A., & Tipton, K. D. (2016). The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein. Physiological Reports, 4(15), e12893. https://doi.org/10.14814/phy2.12893
- Centers for Disease Control and Prevention. (2008, October). Anthropometric Reference Data for Children and Adults: United States, 2003–2006 (No. 10). https://www.cdc.gov/nchs/data/nhsr/nhsr010.pdf