You can ask it a few natural ways:

  • How long is this going to take?
  • How much time will this take?
  • What’s the expected timeline?
  • When should I expect this to be finished?
  • Do you have an estimate for how long this will take?

More polite options

If you want to sound professional or respectful, try:

  • Could you give me an estimate of how long this will take?
  • Do you have a projected timeline?
  • When do you think this might be done?

Short and casual

If you want it simple:

  • How long will this take?
  • Any idea how long this’ll take?

Best all-purpose phrase

A very natural, safe choice is:

Could you give me an estimate for how long this will take?

If you want, I can also give you:

  • a more polite version ,
  • a more casual version , or
  • a version for texting, work, or customer service.