Syllable counter
Type something and the most frequent words show up here.
Syllables are estimated by counting vowel groups and discarding a silent trailing "e". That is right for the large majority of ordinary English words and wrong for a stubborn minority, which is a limit of English spelling, not of the tool.
How to count syllables
No algorithm gets this exactly right, because English spelling does not determine syllable count. The vowel-group rule handles "com-pu-ter" and "ta-ble" correctly and then fails on the standard counterexamples: "business" is two syllables but scans as three, "poem" is two but looks like one, and "fire" divides differently depending on the accent saying it. Dictionaries disagree with each other on a surprising number of words for the same reason. Treat the number as a fast approximation for readability work and as a starting point for anything metrical, where your ear is the authority.
Questions
Good on the large majority of ordinary words and wrong on a stubborn minority. Words like "business", "poem" and "fire" defeat every spelling-based rule.
Yes, type just that word. The syllable figure is the one to read.
Because syllable division depends on pronunciation, which varies by accent. There is genuinely no single right answer for some words.
As a check, yes. For the final version, read it aloud. The ear is the authority for anything metrical.
No. The rule is built around English vowel groups and will be wrong elsewhere.