What's the real estimate of travelling to different planet just like how we can travel to a different city with current technology?

The realistic estimate, is possibly never, unless/until we learn something that we do not know yet, about how to exceed the speed of light, or travel without moving across the intervening distance.

But since we don’t know if/when we’ll make such a discovery, we can’t estimate when or if we will actually make such a discovery, let alone when that would lead to whatever potential technology we don’t know about yet.

There are a few ideas. For example, the Alcubierre Warp Drive idea. But it has many unknown-if-they-are-solvable problems. Such as, it would seem to take more energy than exists in the known universe, to get it to work. Minor delays expected.

(And that’s optimistically assuming we don’t eliminate ourselves with global climate change, and/or simply by causing life as we know it to cease living due to all the things industry and agriculture and land use etc do that are driving species to extinction, wiping out the ecosystems that we too need to live.)

Let’s ignore how long it would take to actually set up a colony and all the other logisitics.
Here’s some math that tconsideres just the travel time using technology as we know it today.
I will use round numbers in English units (because I remember them) .
A light year is 6 trillion miles. The nearest star is 4.2 light years away so the total distance to the nearest star and presumably the nearest planet outside out solar system is 25 trillion mile.
Voyager is the fastest craft made and is moving at 60,000 mph.
25 trillion / 60000mph = 400,000,000 hours = 45,000 years.
Maybe there will be some as yet unknown technology in the intervening years but I would not hold my breath.

In space you change acceleration by producing thrust. Producing thrust requires fuel. Fuel has mass. The more mass you have, the more thrust is required to change acceleration.

That’s a problem, because there’s diminishing returns with larger rockets or if you need to carry more mass for whatever reason.

You can shed mass by using multiple rocket stages: the containers of fuel and entire engines are dumped when no longer needed.

You could potentially refuel in low-Earth orbit.

You can also gain acceleration for “free” with gravity assists around planets like Jupiter and Saturn, which would be enough to kick a spacecraft toward interstellar space and another star system.

Regardless, it would take many thousands of years to reach the nearest star system with current technology. Also no one would survive the journey

I think the question is like asking the engineers and shipbuilders of the 1500’s “ok we’ve got ships that can sail around the oceans, how many more years until we can build a ship that can fly?” 1,000 years? 1,000,000 years? never? I don’t think there’s a clear and obvious path towards that goal, so it’s impossible to extrapolate any kind of timeline.

The distances between the planets needs to be considered. If I have this correctly, if travelling at about 17,000 MPH, it would take 14 months to get to Mars.
If you were to travel to the sun from the Earth at 1000 MPH, it would take you 10 years.
If you were to travel from Pluto to the sun at 1000 MPH, it would take you 450 years.

If humans figure out how to live in space long enough to reach an extra solar planet we would have negated the need to go there. We can just live in space

Thanks for the answers.