How many syllables in weighed?

Two, but pronounced as one.

I think it's one syllable because it's pronounced as one sound: "way'd"

However, "weighed" is composed of two morphemes: "weigh" and "ed"
https://www.grammarbank.com/phoneme-and-morpheme.html

To determine the number of syllables in a word like "weighed," we can follow a simple rule: each vowel sound in a word typically represents one syllable.

In the word "weighed," we have two vowel sounds: "ei" and "ed." The "ei" combination represents one vowel sound, and the "ed" represents another. Therefore, the word "weighed" has two syllables.

Here's a breakdown of the word:
- "Way" has one syllable.
- "Ed" has one syllable.

So, in total, the word "weighed" has two syllables. Remember, this rule applies in most cases, but there are exceptions and variations in pronunciation.