The starting point to determine how much depreciation you can claim on a business asset is a value for the asset known as its "tax basis."
Usually, the tax basis is equal to the asset's purchase price, minus any discounts and plus any sales taxes, delivery charges, and installation fees.
For real estate, you can also include costs of legal and accounting fees, revenue stamps, recording fees, title abstracts/insurance, surveys, and real estate taxes assumed for the seller. Some special rules apply to trade-ins of business equipment.
If you acquire property by gift, the tax basis for depreciation will be the same as the donor's basis at the time of the gift.
If you convert personal property to business use, the basis will be the lower of (a) the fair market value at the time of the conversion, or (b) the cost plus any additions or improvements, and minus any deducted casualty losses, up to the time of the conversion.
Things aren't always so simple. You may need to make some adjustments, under a number of different circumstances: