In US culture, weight is a very sensitive subject and we try to be as delicate as possible when asking about it. These examples are the most careful and polite ways I could think of to ask this question. Of course, in some situations, this question is clearly necessary. If you're filling out a form for someone, you can ask lots of questions very simply: "Height? Weight? Eye color? Hair color?"
Have a great day!
These are the usual ways to ask someone's weight. However, obesity is quite common in the UK and people are sometimes quite sensitive about telling people what their weight is and so it's not usually a topic that is discussed unless you know this person quite well.
A "What's your weight?"
B "I'd rather not say."
誰かの体重を尋ねるときの一般的な言い方です。しかし、UKでは肥満は珍しいことではなく、自分の体重を教えるのが嫌な人も多いです。
そのため、すごくよく知った人に対してなどに限られる話題でもありますね。
A "What's your weight?" 体重何キロ？
B "I'd rather not say." 教えなーい！
A: How much do you weigh?
B: I weigh 65 kilograms
A: What is your weight?
B: I weigh 80 kilograms
例１
A: How much do you weigh?（あなたの体重はどれくらいですか？）
B: I weigh 65 kilograms（65キログラムです）
例２
A: What is your weight?（あなたの体重は？）
B: I weigh 80 kilograms（80キログラムです）
How tall are you? - this is asking the persons height.
What is your weight? - this is asking how much do they weigh.
What is your BMI? - Body mass index - this takes into account height, weight, fat, exercise etc.
How tall are you? これは人の身長を訪ねています。
What is your weight? - これはどれくらいの体重かを尋ねています。
What is your BMI? - 体格指数 - 身長、体重、脂肪、運動などが考慮されます。
You can ask :
"How much do you weigh?"
"What is your weight?"
for length
"What is your length?"
"How tall are you?"
次のように質問できます。 :
"How much do you weigh?"
体重はどのくらいですか？
"What is your weight?"
体重はどのくらいですか？
背の高さは
"What is your length?"
背の高さはどのくらいですか？
"How tall are you?"
背の高さはどのくらいですか？
We can simply ask 'how much do you weigh?' or 'what is your weight?' to discover how much a person may weigh.
We can also ask how many kilograms (kg) or stones someone weighs, depending on what measurement system the country you are in uses.
相手の体重を知りたいときは、シンプルに 'How much do you weigh?'（体重はどのくらいですか）または 'What is your weight?'（同）と言えます。
その国でどの測定単位が使われているかによって、'How many kilograms/stones are you?'（体重は何キロ／ストーンですか）のような言い方もできます。
When asking a male for their weight, you can say:
"How much do you weigh?"
If you are asking a female, you should be more polite, and therefore you can say:
"Do you mind me asking your weight?"
男性に体重を聞くなら、
"How much do you weigh?"（体重はどのくらいですか）
と言えます。
女性に体重を聞くときは、もっと丁寧に言った方がいいです。
例えば：
"Do you mind me asking your weight?"（体重を伺ってもいいですか）
If you would like to know how much someone weighs the sentences above can be used.
There are different weighing measurements used all over the world.
If we are using kilograms (kg) we can ask how many kilograms someone weighs.
Some people feel it is rude to ask how much someone weighs, in this case, you can first say "If you don't mind me asking, I'd like to know how much you weigh?"
相手の体重を知りたいなら、上記の文が使えます。
重さの単位は国によって異なります。
もしキログラムを使っているなら、'How many kilograms do you weigh?'（体重は何キロですか）と言えます。
人に体重を聞くのは失礼と考える人もいます。その場合は、まず始めに、
"If you don't mind me asking, I'd like to know how much you weigh?"（もしよければ、体重を教えていただけますか）
と言えます。
日本 
アメリカ合衆国 
イギリス 
南アフリカ 
