too vs two

The core difference

Two is a numeral and does nothing else. Too is an adverb with two senses — addition and excess — and never refers to a quantity you could count.

Using each one

• Two: Two of the lifts are out of service. It cost two hundred pounds.
• Too (also): He's a decent cook, and a good baker too.
• Too (excessively): That's too big a risk. I stayed up too late.

Two tests, one each

Try the digit 2. 'Two of the lifts' → '2 of the lifts' works, so two is correct.

Try 'also' or 'excessively'. 'Excessively loud' works, so 'too loud' is correct. The two tests never both pass on the same word, which makes this pair easy to settle once you stop and check.

The memory trick

Look at the letters. Two shares its tw with twin, twice, twelve and between — all pair words. Too has an extra O because it is the word about more.

Where they collide

Real confusion is rare, because the meanings are so far apart, but the pair shows up in phrases where both are plausible on first glance:

• 'Two many people' should be 'too many people' — it is an excess, not a count of 2.
• 'Me two' should be 'me too'.
• 'Too of them left' should be 'two of them left'.

Watch for a sentence where both appear: 'The other two were too heavy to carry.' Getting one right and the other wrong is the usual outcome of typing quickly.

The third one

Complete the set with to, the preposition and infinitive marker: 'to the station', 'to explain'. When neither the digit test nor the 'also' test passes, to is what you need. Running all three checks takes about two seconds and catches the mistake before anyone else does.