Replacing an existing tub or shower with a walk-in tub is a home upgrade that can be worthwhile for older adults or anyone with mobility issues, but it’s not as simple as swapping one tub for another.

Most homeowners pay between $5,000 and $30,000 total for a walk-in tub and professional installation. Basic models with simple installation may cost around $3,000 to $8,000, while midrange tubs with ...