Is it "bigger then" or "bigger than"?
"Bigger than." Any comparison uses than.
Contexti
Any adjective ending in -er (bigger, faster, cheaper) is a comparative, and comparatives almost always take than. The same goes for more and less phrases (more expensive than, less crowded than). If the sentence is measuring one thing against another, than is the word.
A little moreii
A comparison measures one thing against another — bigger, smaller, cheaper, older. All of them take than. The only reason to reach for then is if the sentence marks a moment or a sequence.
Examplesiii
This box is bigger then that one.
This box is bigger than that one.
*Bigger* is a comparative → *than*.
The flight was longer then I expected.
The flight was longer than I expected.
Comparing expected vs actual length → *than*.
Watch foriv
If you follow the comparison with a time marker — it was bigger, then it shrank — the second word is actually then, because it marks a new event in a sequence. A comma usually signals that shift.
The full entryv
Time versus comparison — two different jobs, one letter apart.