Straight line

1. A basis of allocating total costs or income equally across successive time periods.

For example, a fixed asset has a cost of $12m, an expected disposal value of $2m and an expected useful life of 4 years. The total expected accounting cost = $12m - $2m = $10m.

Allocated on a straight line basis over 4 years, the depreciation charge in each year would be $10m/4 = $2.5m.

The net book value of the fixed asset would be (at the end of each year): Year 1 = 12.0 - 2.5 = $9.5m. Year 2 = 9.5 - 2.5 = $7.0m. Year 3 = 7.0 - 2.5 = $4.5m. Year 4 = 4.5 - 2.5 = $2.0m.

Using a straight line basis of depreciation, the net book value of a retained asset will often fall to zero. (But it would never be depreciated to a negative value of course.)

2. An estimation method which assumes a straight line relationship between the items under review. Sometimes known as Linear interpolation.

See also

• Depreciation
• Linear interpolation
• Reducing balance
• Sum of the digits