How rental depreciation works
Residential rental buildings in the US are depreciated straight-line over 27.5 years (commercial: 39 years). Land never depreciates, so first remove the land value: depreciable basis = (price × (1 − land %)) + capitalized closing costs + improvements. Annual depreciation = basis ÷ 27.5.
Mid-month convention
Residential property is treated as placed in service in the middle of its month. A property placed in service in January gets 11.5 months of depreciation in year one; one placed in service in December gets 0.5 months. The schedule continues until the basis is fully used, so the schedule spans 28 or 29 calendar years.
Recapture
When you sell, depreciation taken is generally taxed as unrecaptured Section 1250 gain (up to 25%) — see the 1031 exchange calculator for deferring it.