it is ... to doing (do)

Is it "to do" or "to doing"? Decide by the job that to is doing. If to marks the infinitive (purpose, intention), follow it with the base verb: to + do. If to is a preposition, it takes a noun or noun-like form, usually a gerund: to + doing.

Below: a clear diagnostic, concise rules, many wrong→right pairs, and rewrite templates for work, school, and casual sentences so you can fix sentences quickly.

Quick answer

If you can replace to with "in order to" and the sentence still makes sense, use the infinitive (to + base verb). If to follows an adjective, noun, or fixed phrase (committed to, look forward to, used to), treat it like a preposition and use the gerund (to + -ing).

Infinitive: I want to leave / She hopes to win = to + base verb.
Prepositional to: I'm committed to leaving / They're used to winning = to + gerund.
Quick test: Try inserting a pronoun after to (to it/to the). If that fits, use -ing: "committed to it" → "committed to finishing it."

Core explanation (short grammar)

Two roles of to matter here: (1) infinitive marker - to + base verb for purpose, plan, intention; (2) preposition - to + noun phrase. When the noun names an action, use the gerund (to + -ing).

Watch for trigger structures: adjectives/nouns + to (committed to, opposed to, used to) and prepositional verbs (look forward to, object to, admit to).

Infinitive signals: want to, plan to, decide to, hope to, expect to.
Prepositional to (use gerund): look forward to, be used to, be committed to, object to, admit to, be opposed to.
Example contrast: "They plan to hire two engineers." vs "They are committed to hiring two engineers."

Two quick diagnostic tests

Before you edit, try these checks:

Replace to with "in order to." If the sentence still makes sense, keep the infinitive.
Insert a noun or pronoun after to (to it/to the). If that fits, treat to as a preposition and use the gerund.

Test 1: "She left to finish the report" → "She left in order to finish" (infinitive).
Test 2: "She is committed to finishing the report" → "committed to it" works (preposition → gerund).
Wrong → Right:
Wrong: I'm looking forward to meet you. Test: "in order to meet" fails →
Right: I'm looking forward to meeting you.

Common wrong → right pairs (high-frequency traps)

Short, realistic mistakes followed by the correct form. Use the diagnostic tests if you're unsure.

Wrong: I'm looking forward to meet you.
Right: I'm looking forward to meeting you.
Wrong: She is accustomed to to drive on the left.
Right: She is accustomed to driving on the left.
Wrong: They are committed to improve customer service.
Right: They are committed to improving customer service.
Wrong: He objected to accept the offer.
Right: He objected to accepting the offer.
Wrong: We plan to launching the product in June.
Right: We plan to launch the product in June.
Wrong: She admitted to steal the documents.
Right: She admitted to stealing the documents.
Wrong: I'm opposed to change.
Right: I'm opposed to changing the policy.
Wrong: He decided to going home early.
Right: He decided to go home early.
Wrong: I used to go jogging every morning (intended: 'accustomed to').
Right: I am used to jogging every morning.
Wrong: She hopes to studying medicine.
Right: She hopes to study medicine.
Wrong: He objected to change the rules.
Right: He objected to changing the rules.
Wrong: I'm committed to help the team.
Right: I'm committed to helping the team.

Rewrite help: work, school, and casual examples

Use these paired rewrites as templates when you edit sentences in similar contexts.

Work - Wrong: The team is committed to deliver results by Q3.
Rewrite: The team is committed to delivering results by Q3.
Work - Wrong: I plan to attending the conference next month.
Rewrite: I plan to attend the conference next month.
Work - Wrong: We look forward to discuss partnership opportunities.
Rewrite: We look forward to discussing partnership opportunities.
School - Wrong: Students are allowed to bringing one sheet into the exam.
Rewrite: Students are allowed to bring one sheet into the exam.
School - Wrong: The author is opposed to change the policy without consultation.
Rewrite: The author is opposed to changing the policy without consultation.
School - Wrong: She used to studying late every night (meant: accustomed).
Rewrite: She is used to studying late every night.
Casual - Wrong: I'm looking forward to meet you this weekend.
Rewrite: I'm looking forward to meeting you this weekend.
Casual - Wrong: Are you used to to wake up so early?
Rewrite: Are you used to waking up so early?
Casual - Wrong: I want to going to the party, but I'm tired.
Rewrite: I want to go to the party, but I'm tired.

Fix-it checklist: 5 quick steps

Follow these steps, then read the sentence aloud to check flow and meaning.

1) Identify the verb immediately after to.
2) Replace to with "in order to." If it works, use the infinitive (to + base verb).
3) If to follows an adjective, noun, or fixed phrase (committed to, used to, look forward to), use -ing.
4) If both forms are possible (begin, start), choose the form that fits your tone; both are usually acceptable.
5) Read aloud to ensure the meaning didn't change.

Rewrite:
Original: She wants to improving her skills. Check: "in order to improving" fails →
Correct: She wants to improve her skills.
Rewrite:
Original: We're committed to improve patient outcomes. Check: "committed to it" works →
Correct: We're committed to improving patient outcomes.
Rewrite: He began to study / He began studying - both acceptable; pick the rhythm that sounds right.

Try your own sentence

Test the whole sentence in context. The two quick tests usually give a clear answer.

Real usage: meaning shifts when you change form

Changing between infinitive and gerund can change meaning. Watch these contrasts.

stop to + infinitive = pause in order to do something; stop + -ing = quit the activity.
used to + base = past habit; be used to + -ing = accustomed to something now.
try + infinitive = attempt; try + -ing = experiment to see the result.

Usage: I stopped to smoke. (I paused what I was doing so I could smoke.) vs I stopped smoking. (I quit smoking.)
Usage: I used to run every day. (past habit) vs I am used to running every day. (I'm accustomed to it.)
Usage: Try to reboot the system. (attempt) vs Try rebooting the system. (suggestion/experiment)

Memory trick, similar mistakes, and verb lists

Memory trick: Ask "to = in order to?" If yes → infinitive. If no, and the word before to is an adjective, noun, or fixed phrase → gerund.

Common confusions: mixing "used to" (past habit) with "be used to" (accustomed), "stop to" vs "stop -ing," and the extra "to" error ("used to to").

Requires gerund after to: look forward to, be used to, be committed to, object to, admit to, be opposed to.
Accepts both forms (little meaning change): begin, start, continue, like (context-dependent).
Change meaning between forms: stop, remember, forget, try.

Wrong: I'm used to to swim.
Right: I'm used to swimming.
Wrong: He stopped to smoke (if you mean 'quit').
Right: He stopped smoking.
Usage: Begin/start: "She began to cry" / "She began crying" - both fine; pick tone.

Hyphenation, spacing, and punctuation when you edit

When you fix to + verb forms, also check spacing, hyphens, and commas so the rewrite reads cleanly.

Never hyphenate "to" and the following verb. Only "to-do" (hyphenated) is a noun meaning 'task list'.
Correct spacing: "to do", "to doing". Incorrect: "to-doing" or "todoing".
If the sentence grows long after rewriting, consider splitting it or adding a comma for clarity.

Usage: Correct: I need to finish this report.
Incorrect: I need to-finish this report.
Usage: Correct noun: a to-do list. Not: a to do list (hyphenated form is standard: to-do list).

Grammar notes: exceptions and verbs that behave differently

Use this when you see verbs that allow both forms or where meaning shifts. If in doubt, check the verb's meaning in context.

Both forms usually acceptable (no major meaning change): begin, start, continue.
Both forms acceptable with style differences: like, love, hate (I like to swim / I like swimming).
Different meanings: remember to do (don't forget) vs remember doing (recall); stop to do (pause) vs stop doing (quit).

Usage: Remember to lock the door. (Don't forget.) vs I remember locking the door. (I recall doing it.)
Usage: Try to open the file. (attempt) vs Try opening the file. (experiment).

FAQ

Should I always use "to + -ing" after "committed to"?

Yes. In "committed to" the to is a preposition, so use the gerund: "committed to improving."

Which "used to" is followed by -ing and which by the base verb?

"Used to" + base verb = past habit (I used to swim). "Be used to" + -ing = accustomed to (I'm used to swimming).

If I'm unsure, which test is fastest?

Replace to with "in order to." If that works, use the infinitive. If it doesn't and to follows an adjective/noun or fixed phrase, use the gerund.

Do verbs like "begin" and "start" prefer one form?

No. "Begin" and "start" commonly take either the infinitive or the gerund with little meaning change: "begin to study" / "begin studying." Choose the form that sounds right.

Is "look forward to meet you" ever correct?

No. "Look forward to" is a fixed prepositional phrase and requires a gerund: "look forward to meeting you."

Fix one sentence now

If you're unsure about a sentence, apply the two quick tests above or paste the sentence into a grammar checker that explains the change. Keep a short list of trigger phrases (look forward to, be used to, committed to, object to). Over time you'll spot the pattern instantly.