Depreciation Calculator
Estimate prime cost or diminishing value for one business asset. The schedule follows Australian financial years, 1 July to 30 June, and pro-rates the first year by the days held.
Short answer
An ATO depreciation calculator works out the decline in value of a business asset. For an asset you started to hold on or after 10 May 2006, diminishing value is base value × (days held ÷ 365) × (200% ÷ effective life). Prime cost is cost × (days held ÷ 365) × (100% ÷ effective life). The first year is pro-rated from the start date to 30 June. This estimates one asset. A quantity surveyor's rental-property schedule is a different report.
How it's calculated
Diminishing value, for an asset you started to hold on or after 10 May 2006, is base value × (days held ÷ 365) × (200% ÷ effective life). The base value is the cost in the first year and the opening adjustable value after that. Prime cost is cost × (days held ÷ 365) × (100% ÷ effective life). The divider stays 365 when the income year has 366 days.
Days held include the start date and 30 June. The ATO's example of 1 March 2022 to 30 June 2022 is 122 days. A full year from 1 July is 365 days, or 366 if that financial year includes 29 February. Each year's decline is rounded to the nearest cent and capped at the opening adjustable value.
The ATO's photocopier example is a $1,500 asset with a 5-year effective life, first used on 1 July 2025 and used only for a taxable purpose. Diminishing value for 2025–26 is $600. Prime cost is $300. The ATO's $80,000, 5-year illustration assumes 365 days every year: diminishing value is $32,000, then $19,200, $11,520 and $6,912. Prime cost is $16,000 a year. Held from 1 July 2025, this calculator counts 366 days in 2027–28, so the third diminishing-value claim on that $80,000 asset is $11,551.56.
On a $10,000 asset with a 4-year effective life, prime cost and a start date of 1 January 2026 (181 days in 2025–26), the first-year decline is $1,239.73. Later years use the real length of each financial year, and the last year claims the remaining cost. The schedule below adds back to $10,000.00.
For 2026–27 the instant asset write-off threshold is $20,000. The ATO says this measure is now law and is permanent from 1 July 2026 for a small business with aggregated turnover under $10 million that uses the simplified depreciation rules. Each eligible asset must cost less than $20,000 and be first used, or installed ready for use, in the income year. This schedule shows the general formulas. It leaves that write-off, and the small business pool rate of 15% then 30%, for you to apply when they fit.
The result assumes the asset is used only for a taxable purpose. Private use reduces the deduction. Assets you held before 10 May 2006 use a 150% diminishing value formula, which this calculator does not apply. A quantity surveyor's rental-property schedule is a different report. This page estimates one business asset.
| Financial year | Days held | Decline in value | Closing value |
|---|---|---|---|
| 2025–26 | 181 | $1,239.73 | $8,760.27 |
| 2026–27 | 365 | $2,500.00 | $6,260.27 |
| 2027–28 | 366 | $2,506.85 | $3,753.42 |
| 2028–29 | 365 | $2,500.00 | $1,253.42 |
| 2029–30 | 365 | $1,253.42 | $0.00 |
Checked 11 November 2026 against the ATO:
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