Formulas
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Straight-Line (SL)Annual depreciation = (Cost − Salvage) ÷ Life
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Declining Balance (DB, general)
Rate = Factor ÷ Life (Factor commonly 1.25, 1.5, or 2)
Depreciation for a year = Rate × Book value at start of year
Stop at (or switch to SL to reach) Salvage. -
Double Declining Balance (DDB)
Depreciation for a year = (2 ÷ Life) × Book value at start of year
Do not depreciate below Salvage. -
Sum-of-Years-Digits (SYD)Sum of digits = N × (N + 1) ÷ 2, where N = Life in yearsDepreciation for a year = (Remaining life ÷ Sum of digits) × (Cost − Salvage)
Example
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SL year 1: 9,000 ÷ 5 = 1,800
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DDB year 1: (2 ÷ 5) × 10,000 = 4,000
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SYD year 1: (5 ÷ 15) × 9,000 = 3,000
(Results continue annually until the book value reaches the salvage value.)
Tips
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Use SL for a simple, even expense each year.
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Use DDB/DB or SYD to front-load expense when assets lose value faster early on.
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Switch from DDB/DB to SL near the end to avoid dropping below Salvage.
How to Use the Depreciation Calculator
Follow these steps to enter asset details and calculate annual depreciation and ending book value across methods.
Select the depreciation method.
Choose Straight-Line for equal yearly expense, Declining Balance or Double Declining for accelerated expense, or SYD for a front-loaded schedule. Switching methods changes how the annual charge is computed. A common mistake is using an accelerated method when your policy requires straight-line.
Enter the asset cost.
Type the full capitalized cost (purchase price plus setup/shipping you capitalize). Use plain numbers in your currency (e.g., 10000.50). Do not include financing interest or maintenance costs.
Enter the salvage (residual) value.
Input the expected value at the end of the useful life (e.g., 1000). It must be less than the asset cost; entering a higher salvage will yield zero or negative depreciation.
Enter the useful life (years).
Provide the service life as whole years or decimals if applicable (e.g., 5 or 1.5 for 18 months). Life must be greater than zero; convert months to years before entering.
Review results and adjust decimals.
Check Year 1 Depreciation, Total Depreciation (should equal cost minus salvage), and Book Value at End of Life (should equal salvage). Use the “Show Decimals” toggle to control rounding; rounded outputs can differ slightly from unrounded schedules.
Frequently Asked Questions
What does the Straight-Line (SL) method compute and what is the formula?
SL spreads the depreciable amount evenly. Formula: annual depreciation = (cost − salvage) ÷ useful life. Example with cost 10000, salvage 1000, life 5: (10000 − 1000) ÷ 5 = 1800 per year.
How is the (single) Declining Balance (DB) method calculated?
DB uses a constant rate applied to the opening book value each period, chosen to reach the salvage value over the useful life. Rate formula: r = 1 − (salvage ÷ cost)^(1 ÷ life). Annual depreciation in year t: depreciation_t = r × book value at start of year t. Book value must not fall below salvage.
How does Double Declining Balance (DDB) work?
DDB accelerates depreciation at rate 2 ÷ life applied to opening book value. Formula: depreciation_t = (2 ÷ life) × opening book value. Do not depreciate below salvage; when straight-line on the remaining depreciable amount over remaining life is greater than DDB for a year, switch to straight-line for the remainder.
What is the Sum-of-Years’-Digits (SYD) formula?
Compute S = life × (life + 1) ÷ 2. In year t (t = 1 is first year), remaining-life factor = (life − t + 1) ÷ S. Annual depreciation = remaining-life factor × (cost − salvage). Total depreciation over the full life equals (cost − salvage).
How are totals, book value, and “Avg Annual Depreciation (% of depreciable base)” reported?
Total depreciation = sum of annual charges, capped at (cost − salvage). End-of-life book value = max(salvage, cost − total depreciation). Average annual depreciation (% of depreciable base) = [ (total depreciation ÷ life) ÷ (cost − salvage) ] × 100%, which equals 100% when summed over the full life.
Computations accept cost, salvage (residual) value, and useful life (years). Methods implemented: Straight-Line, Declining Balance (constant-rate to reach salvage), Double Declining Balance (rate = 2 ÷ life with a switch to straight-line when it yields a larger period charge and with a floor at salvage), and Sum-of-Years’-Digits (denominator S = n(n+1)/2; yearly fraction = remaining years ÷ S).
Monetary results use ISO 4217 currency codes for labeling; numerical rounding follows NIST guidance using round-half-even at the display precision while retaining higher internal precision to avoid cumulative bias. Units follow SI conventions for any non-monetary quantities. Unless specified, a full-year convention is assumed (no partial-period proration). Constraints: book value never drops below salvage; total depreciation over life is limited to (cost − salvage).
Sources & Methodology