Short answer
The Prophet ﷺ said Allah created Adam sixty cubits tall, roughly thirty metres or about ninety feet. He added that people have kept getting shorter ever since, and that everyone who enters Jannah will have the form of Adam. The hadith does not mention Hawwa's (Eve's) height.
The hadith is in Sahih al-Bukhari and Sahih Muslim, so Sunni scholars accept it. It is part of the unseen, believed on the strength of a reliable report, even though it is not something we can measure today.
The four schools agree on this.
Explanation
The Prophet ﷺ said: "Allah created Adam, and his height was sixty cubits." Allah then told him to greet a group of angels and listen to their reply, which would be his greeting and his children's. Adam said: as-salamu alaykum. They replied: as-salamu alaykum wa rahmatullah. He then said that everyone who enters Paradise will be in the form of Adam, and that creation has kept decreasing until now.
A cubit is the length from the elbow to the fingertips, about forty-five to fifty centimetres, so sixty cubits is roughly twenty-seven to thirty metres. The hadith does not say how quickly people became shorter, or give Hawwa's height. Anything beyond what the hadith says is guesswork.
Some ask how this fits with the remains of ancient peoples, who were not giants. Ibn Hajar raised this very question in his commentary on al-Bukhari, noting that the dwellings of Thamud do not suggest very tall people, and said he had not found an answer that removed the difficulty. Some later scholars suggested that the decrease happened over a long time before those peoples, and all agree that a sahih report is not rejected because we cannot yet explain it.
The hadith also teaches the origin of the Islamic greeting and that the people of Jannah will be perfect in form: "We have certainly created man in the best of stature" (95:4). See the story of Prophet Adam, how Eve was created and the meaning of assalamu alaikum.
The evidence
Quran, Surah At-Tin 95:4
لَقَدْ خَلَقْنَا ٱلْإِنسَٰنَ فِىٓ أَحْسَنِ تَقْوِيمٍۢ ﴿٤﴾
We have certainly created man in the best of stature;
Shows the excellence of the human form.
Sahih al-Bukhari 3326
Sahih... خَلَقَ اللَّهُ آدَمَ وَطُولُهُ سِتُّونَ ذِرَاعًا ...
"Allah created Adam, and his height was sixty cubits."
The source for Adam's height.
Sahih al-Bukhari 3326
Sahih... فَكُلُّ مَنْ يَدْخُلُ الْجَنَّةَ عَلَى صُورَةِ آدَمَ، فَلَمْ يَزَلِ الْخَلْقُ يَنْقُصُ حَتَّى الآنَ ...
"Everyone who enters Paradise will be in the form of Adam, and creation has kept decreasing until now."
Shows that people became shorter over time.
Where the ruling is recorded
- Fath al-Bari (Ibn Hajar), Book of the Prophets, the hadith on the creation of Adam. Discusses the hadith and the question of ancient remains.
- Umdat al-Qari (Badr al-Din al-Ayni), Book of the Prophets, the creation of Adam. The Hanafi commentary on al-Bukhari explains the hadith.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.