Straight-Line Book Depreciation Calculator

Read the calculator result

This calculator spreads an asset’s depreciable book cost evenly over the useful life you enter. It shows annual and monthly depreciation, accumulated depreciation after a selected number of full months, the remaining book value, and the amount still available to depreciate. It’s a simple book-accounting model with explicit assumptions.

Use it to understand a fixed-asset schedule, estimate an expense allocation, or compare reasonable residual-value and useful-life assumptions. It doesn’t calculate a federal tax deduction, select a tax recovery period, or estimate what someone would pay for the asset today. The displayed book value follows the entered accounting assumptions.

Straight-line depreciation: start with the recorded asset cost

Enter the capitalized cost assigned to the asset in the records you’re modeling. This may differ from the amount financed, the cash down payment, or the remaining loan balance. The calculator depreciates the asset-cost input; it doesn’t create a loan schedule or determine which acquisition expenditures should be capitalized.

Penn State’s straight-line depreciation lesson explains the method using cost, residual value, and useful life. It describes cost as the amount associated with obtaining the asset and preparing it for use, and residual value as the estimated amount left at the end of the intended use. Confirm the appropriate recorded amounts before entering them.

If a purchase contains several assets with different estimated lives or residual values, calculate them separately. Combining a computer, furniture, and another piece of equipment into one arbitrary life can conceal how the individual schedules differ. Keep the asset identifier and supporting cost record alongside each saved calculation so a later reviewer can trace the input.

Choose residual value and useful life deliberately

Residual value is the amount you choose to leave undepreciated at the end of the modeled life. It’s also called salvage value in many discussions. The form requires it to be no greater than cost. A residual equal to cost produces no depreciable amount; a zero residual allows the entire entered cost to be allocated over the selected life.

Useful life is entered in whole years and converted to twelve equal monthly periods per year. Choose the life for the book scenario you’re analyzing; the form doesn’t retrieve an industry estimate or a tax table. A longer life spreads the same depreciable amount over more periods and therefore reduces the expense per period.

The elapsed-month field counts full depreciation months already included in the schedule. It isn’t a purchase date. Month zero means no depreciation has yet been allocated. Eighteen means eighteen complete equal months. The calculator doesn’t infer whether an acquisition month should count as a full month, half a month, or another convention.

How the calculator works

Depreciable base = asset cost − residual value. Annual depreciation = depreciable base ÷ useful life in years. Monthly depreciation is that annual amount divided by twelve. These formulas produce the same unrounded expense for each complete month within the entered useful life.

The months used for accumulated depreciation are the smaller of elapsed months and the useful life expressed in months. Accumulated depreciation = monthly depreciation × months depreciated. Book value = asset cost − accumulated depreciation. The remaining depreciable base is the original depreciable base minus accumulated depreciation.

This cap prevents depreciation from continuing indefinitely. Once the full useful life has elapsed, accumulated depreciation equals the depreciable base and book value equals residual value. The result doesn’t fall below residual merely because a larger elapsed-month count was entered.

Straight-line depreciation calculator example: a $30,000 asset after eighteen months

Suppose an asset has a recorded cost of $30,000, an estimated residual value of $5,000, and a five-year useful life. The depreciable base is $25,000. Dividing that amount by five years gives $5,000 per year, or approximately $416.67 per month when displayed to cents.

The $22,500 book value includes both the $17,500 not yet depreciated and the $5,000 residual amount that this model leaves in place. Confusing remaining depreciable base with book value would omit the residual and understate the displayed carrying amount by $5,000.

Monthly expense is retained internally as $416.666666… rather than rounded to $416.67 before multiplication. Multiplying the displayed $416.67 by eighteen gives $7,500.06, while the model’s unrounded calculation gives $7,500.00. An accounting system that posts rounded cents each month may need a final-period adjustment to reconcile its complete schedule.

Read the schedule across the full useful life

The chart shows book value declining evenly across the entered life. It includes the selected elapsed point within that life, and the accompanying table provides the values without requiring you to read the image. For the default example, the year-end amounts follow this schedule.

Entering seventy-two elapsed months still produces $25,000 of accumulated depreciation and $5,000 of book value. Only sixty months are depreciated. The asset may still be used, sold, or disposed of in a real business, but those events aren’t automatically represented by extending this mathematical schedule.

Compare assumptions without rewriting an existing schedule

To see the effect of residual value, change the example’s residual to zero while keeping the $30,000 cost and five-year life. Annual depreciation becomes $6,000, monthly depreciation becomes $500, and accumulated depreciation after eighteen months becomes $9,000. Book value at that point is $21,000, which is $1,500 lower than under the original assumptions.

To examine useful life instead, restore the $5,000 residual and change the life to ten years. Annual depreciation becomes $2,500. After eighteen months, accumulated depreciation is $3,750 and book value is $26,250. The same $25,000 depreciable base is being allocated more slowly; the asset’s purchase price hasn’t changed.

These comparisons recalculate the whole model from month zero. They don’t implement an accounting change of estimate midway through an existing asset’s life. If a recorded asset needs a revised residual or remaining useful life, preserve the historical record and determine the appropriate treatment before changing its continuing schedule.

Separate depreciation from cash flow and resale value

The periodic expense is an allocation of the entered cost. The calculator doesn’t subtract cash from a bank account each month or set aside a replacement fund. If the asset was purchased with cash, the purchase payment and later depreciation entries describe different things. If it was financed, scheduled principal and interest payments also require their own cash-flow model.

When using the cash runway calculator, enter the relevant cash outflows rather than adding this noncash monthly allocation as another cash payment. Counting both the purchase payment and depreciation as separate payments would overstate the modeled cash consumed by the asset.

Book value is also not a resale quote. An asset can have a market value above or below its calculated carrying value. The form doesn’t examine condition, demand, maintenance, selling costs, impairment, or a later improvement. If you need a value for the net worth calculator, use a valuation basis appropriate to that statement rather than assuming this book figure is a current market price.

Keep tax depreciation separate

IRS Publication 946 explains federal depreciation rules, including MACRS, recovery periods, conventions, and other deduction provisions. Those rules are outside this calculator. An entered five-year book life doesn’t establish the correct tax classification or deduction schedule for a particular asset.

The calculator doesn’t calculate Section 179 deductions, bonus depreciation, tax basis adjustments, business-use limitations, or disposition consequences. It also doesn’t implement impairment or revaluation under a financial-reporting framework. Use the result for the clearly defined straight-line book scenario and obtain the relevant treatment separately when preparing formal records or a tax return.

Check the schedule before using it

Keep the cost record, residual assumption, useful-life rationale, start convention, and elapsed-month count together. Reconcile book value plus accumulated depreciation to original cost. Reconcile remaining depreciable base plus accumulated depreciation to the original depreciable base. Both relationships should hold at every point in this model.

Then compare the calculation with the actual ledger or schedule you intended to review. Differences can come from partial periods, prior rounded entries, changed estimates, additional capitalized amounts, or events this form doesn’t model. Identify the cause before treating a difference as a posting error.

Straight-line depreciation calculator questions

Does the calculator start depreciation on the purchase date?

No. You supply full months elapsed. The form has no dates and applies no acquisition-month convention. Establish the appropriate starting point before entering the month count.

Can book value fall below the entered residual?

No. Accumulated depreciation stops at the depreciable base. A later impairment, disposal, or revised estimate would require analysis beyond this fixed-assumption model.

What if cost equals residual value?

The depreciable base and all periodic depreciation are zero. Book value remains at cost for every elapsed month. This follows the inputs and doesn’t independently validate the residual estimate.