Depreciable Base = Cost - Salvage Value

Straight Line Depreciation Expense = Depreciable Base / Useful Life

Assets

– Accumulated Depreciation

Book Value

DDB Depreciation Expense = 2 * (1 / Useful Life) * Book Value

When using DDB, make sure you don't depreciate more than the depreciable base!

Units of Production Depreciation Expense = Units Produced * (Depreciable Base / Total Expected Units)

This is not different than straight line, except that instead of "years", we're using "units".

Partial Year Depreciation Expense = SL or DDB Full Year Expense * Months In Service / 12

When using units of production, there is no "partial year" formula, since UoP is not time based in the first place.

Purchase Price of Asset = Purchase Price of Group * (FMV of Asset / FMV of Whole Group)

Lump Sum Purchases are also called Basket Purchases, or Group Purchases