Depreciating Assets with Excel 2007’s SLN, SYD, DB, and DDB Functions
Excel 2007 lets you choose from four Depreciation functions — SLN, SYD, DB, and DDB — each of which uses a different method for depreciating an asset over time. These builtin Depreciation functions, found on the Financial button’s dropdown menu on the Formulas tab of the Ribbon, include the following:

SLN(cost,salvage,life) to calculate straightline depreciation.

SYD(cost,salvage,life,period) to calculate sumofyearsdigits depreciation.

DB(cost,salvage,life,period,[month]) to calculate declining balance depreciation.

DDB(cost,salvage,life,period,[factor]) to calculate doubledeclining balance depreciation.
As you can see, with the exception of the optional month argument in the DB function and the optional factor argument in the DDB function, all the Depreciation functions require the cost, salvage, and life arguments, and all but the SLN function require a period argument as well:

Cost is the initial cost of the asset that you’re depreciating.

Salvage is the value of the asset at the end of the depreciation (the salvage value of the asset).

Life is the number of periods over which the asset is depreciating (also known as the useful life of the asset).

Period is the period over which the asset is being depreciated. The units that you use in the period argument must be the same as those used in the life argument of the function, so that if you express the life argument in years, you must also express the period argument in years.
Note that the DB function accepts an optional month argument. This argument is the number of months that the asset is in use in the first year. If you omit the month argument from your DB function, Excel assumes the number of months of service to be 12.
When using the DDB function to calculate the doubledeclining balance method of depreciation, you can add an optional factor argument. This argument is the rate at which the balance declines in the depreciation schedule. If you omit this optional factor argument, Excel assumes the rate to be 2 (thus the name doubledeclining balance).
The following figure contains a Depreciation table that uses all four depreciation methods to calculate the depreciation of office furniture originally costing $50,000 to be depreciated over a 10year period, assuming a salvage value of $1,000 at the end of this depreciation period.
The Formula bar shows the SLN formula in cell B9:
=B8SLN($C$3,$C$5,$C$4)
This formula subtracts the amount of straightline depreciation to be taken in the first year of service from the original cost of $50,000 (this value is brought forward from cell C3 to cell B8 with the formula =C3). After creating this original formula in cell B9, you can drag the Fill handle to copy it down to cell B18, which contains the final salvage value of the asset in the 10th year of service.
Cell C9 contains a similar formula for calculating the sumofyearsdigits depreciation for the office furniture. This cell contains the following formula:
=C8SYD($C$3,$C$5,$C$4,$A9)
This formula subtracts the amount of sumofyearsdigits depreciation to be taken at the end of the first year from the original cost of $50,000 in cell C8 (also brought forward from cell C3 with the formula =C3). After creating this original formula in cell C9, you again use the Fill handle to copy it down to cell C18, which also contains the final salvage value of the asset in the 10th year of service.
You use the same basic procedure to create the formulas using the DB and DDB depreciation methods in the cell ranges D8:D18 and E8:E18, respectively. Cell D9 contains the following DB formula:
=D8DB($C$3,$C$5,$C$4,$A9)
Cell E9 contains the following DDB formula:
=E8DDB($C$3,$C$5,$C$4,$A9)
Note that, like the SYD function, both of these depreciation functions require the use of a period argument, which is supplied by the list of years in the cell range A9:A18. Note also that the value in cell C4, which supplies the life argument to the SYD, DB, and DDB functions, matches the year units used in this cell range.