Irish Calculators
Business

Asset Depreciation and Book Value Calculator

Calculate depreciation and remaining book value from cost, residual value, method and service dates. The result follows your accounting assumptions and does not establish a tax allowance or impairment charge.

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How the calculation works

Build an accounting depreciation schedule from asset cost, residual value and service dates. Choose straight-line or reducing-balance charges and see how a partial service year affects accumulated depreciation and net book value.

Straight-line annual charge = (cost − residual) / useful life. Reducing-balance charge = opening book value × rate, capped at residual and trued up in the final year. A partial service year receives its elapsed-day fraction of the annual charge.

  1. Define depreciable cost

    Subtract residual value from asset cost. Enter useful life in whole years and use the in-service date rather than an unrelated invoice or payment date.

  2. Calculate annual charges

    Straight line divides depreciable cost by useful life. Reducing balance applies its percentage to opening value, capped at residual, then clears the remaining depreciable amount in the final year.

  3. Prorate a partial year

    The current partial service year receives its elapsed-day fraction of the annual charge, using actual days between anniversaries. Accumulated charges reduce the asset's net book value.

Worked example: Straight line first year

Sample inputs demonstrate the method. They are not a forecast or product offer.

Cost of €10,000 less €1,000 residual gives €9,000 depreciable over three years, or €3,000 annually. From 1 January 2024 to 1 January 2025, the full-year charge leaves €7,000 net book value.

Depreciation method
Straight line
Asset cost
10000
Residual value
1000
Useful life in whole years
3
In-service date
2024-01-01
Calculate through
2025-01-01

Expected result

Accumulated depreciation
€3,000.00
Net book value
€7,000.00
Worked example: Reducing first two years

Sample inputs demonstrate the method. They are not a forecast or product offer.

Depreciation method
Reducing balance
Asset cost
10000
Residual value
1000
Useful life in whole years
3
Annual reducing-balance rate (%)
40
In-service date
2024-01-01
Calculate through
2026-01-01

Expected result

Accumulated depreciation
€6,400.00
Net book value
€3,600.00

Understanding your result

Net book value is the carrying amount under the supplied assumptions. It is not a market valuation, replacement quote or estimate of eventual sale proceeds.

The schedule is separate from tax allowances. It does not determine the required accounting policy or add impairment, revaluations and disposal adjustments.

Questions you might have

Why is the last reducing-balance charge different?

A fixed percentage may not reach the residual value at the end of useful life. This schedule explicitly writes the remaining amount down in its final year.

Choosing the right inputs

Residual value
Enter the amount remaining at the end of useful life. It cannot exceed cost, and the schedule never depreciates below this floor.
Depreciation method
Straight line spreads depreciable cost evenly. Reducing balance applies the chosen rate to opening book value, with a final-year adjustment to residual.
Calculate through
The calculation date is an exclusive boundary. Exactly one service anniversary after the start includes one complete service year.

Common mistakes to avoid

  • Do not apply the reducing-balance percentage to original cost every year.
  • Do not assume every service year has 365 days; actual anniversary intervals determine the partial-year fraction.

Assumptions to check

  • Use amounts in one currency and one reporting period. Results are labelled EUR; the arithmetic also works for another consistent currency.
  • The chosen useful life, residual value and method are accounting assumptions. The engine does not determine an allowable tax deduction.
  • Leap-day anniversaries fall on 28 February in non-leap years. No revaluation, impairment or disposal gain is modelled.

Sources and method

Read our calculation and testing approach.