A capex to depreciation calculation shows how a capital purchase turns into a yearly accounting expense. In plain terms, you start with what the asset cost, subtract any salvage value left at the end, and spread the remaining amount across its useful life.
That gives you a depreciation estimate you can use for budgeting, planning, and comparing assets. If you also want to compare the result with the time value of money, a present value calculator can help with the finance side, while depreciation itself follows accounting rules rather than market value.
What capex to depreciation means
Capex, short for capital expenditure, is money spent to buy or improve an asset that will be used for more than one accounting period. Depreciation is the part of that asset’s cost that is recognized as an expense each year.
The calculator is useful when you want to answer questions like:
- How much of this purchase becomes an annual expense?
- What is the monthly or yearly depreciation load on the business?
- How much value is being used up each period?
This is not the same as cash flow. The cash goes out when you buy the asset, but the depreciation expense is usually recognized gradually. That is why capex and depreciation often appear in different parts of financial analysis.
The core formula
The most common method behind this calculator is straight-line depreciation. It spreads the depreciable amount evenly over the useful life.
Formula in words
Depreciation per year = (Asset cost − Salvage value) ÷ Useful life
Formula in symbols
\[ D = \frac{C - S}{L} \]
Where:
- \(D\) = annual depreciation
- \(C\) = asset cost
- \(S\) = salvage value
- \(L\) = useful life in years
The depreciable base is:
\[ \text{Depreciable base} = C - S \]
If you also want the depreciation per month, divide the annual amount by 12:
\[ D_{month} = \frac{D}{12} \]
This same framework is often used in planning tools even when the actual accounting method later differs. If you are comparing operating costs with ownership costs, you may also find a car depreciation calculator helpful for a more asset-specific view.
When you would use this calculation
You would use a capex to depreciation calculation when you need a simple estimate of how a purchase affects accounting profit over time. Common uses include:
- budgeting for equipment, machinery, furniture, or software
- estimating annual expense for financial forecasts
- checking whether a planned investment fits a target profit margin
- comparing two assets with different useful lives or resale values
- building a rough depreciation schedule before doing a deeper accounting model
It is especially useful when you know the purchase price and expected end value, but you do not yet want a detailed tax or accounting schedule.
Worked examples
The examples below use hypothetical numbers.
Example 1: basic straight-line depreciation
Suppose an asset costs $50,000, has a salvage value of $5,000, and a useful life of 5 years.
Annual depreciation is:
9,000
The depreciable base is:
45,000
So the asset loses the same accounting value each year under straight-line depreciation. If you want the monthly figure, you can divide the annual amount by 12:
750
This means you would treat the asset as costing $45,000 to use up over its life, not $50,000, because the salvage value is expected to remain at the end.
Example 2: lower salvage value, shorter life
Suppose equipment costs $18,000, salvage value is $2,000, and useful life is 4 years.
Annual depreciation is:
4,000
The depreciable base is:
16,000
This example shows a smaller asset with a faster write-off. Because the useful life is shorter, the annual expense is higher than it would be for the same cost spread over a longer period.
Example 3: high-cost asset with long life
Suppose a machine costs $120,000, salvage value is $20,000, and useful life is 10 years.
Annual depreciation is:
10,000
The depreciable base is:
100,000
If you want the monthly equivalent:
833.33
For planning, this helps you estimate how much of the purchase should be reflected in each year’s operating results rather than treated as an immediate cost.
How to read the result
The result is usually an annual depreciation amount. That means the asset’s cost, excluding salvage value, is being spread evenly across each year of its useful life.
Use the result this way:
- Annual depreciation tells you the yearly accounting expense.
- Monthly depreciation is useful for internal budgets and monthly reporting.
- Total depreciation over the life should equal cost minus salvage value.
- Net book value after a given number of years is original cost minus accumulated depreciation.
A simple check is:
\[ \text{Total depreciation} = C - S \]
If your total depreciation does not match that, then one of the inputs is off or you are using a different depreciation method.
For a broader financial planning comparison, you might also look at a future value calculator if you are thinking about replacement timing or how much money you will need later.
Common mistakes to avoid
Mixing up capex and depreciation
Capex is the purchase itself. Depreciation is the accounting expense over time. They are related, but they are not the same number.
Using cash outlay as depreciation
If you pay $50,000 for an asset, that does not mean $50,000 of depreciation in one year. Under straight-line depreciation, only part of that cost is recognized each year.
Forgetting salvage value
If an asset is expected to have value at the end, you should subtract that value before dividing by useful life. Leaving it out can overstate depreciation.
Using the wrong useful life
The useful life should reflect the period over which the asset is expected to provide value in the business. If you choose a life that is too short or too long, the annual expense will be distorted.
Treating all methods as the same
Straight-line depreciation is simple, but some accounting and tax systems use accelerated methods. Those can produce very different yearly numbers even when the total depreciable amount is the same.
Limits of this calculator
This calculator is best for a straight-line estimate. That makes it practical, but it also means there are limits.
- It does not model accelerated depreciation methods.
- It does not apply tax rules, bonus depreciation, or local accounting standards.
- It does not account for repairs, disposal costs, financing, or inflation.
- It assumes the asset’s salvage value and useful life are known in advance.
That is why the result should be treated as a planning figure unless your accounting policy specifically uses the same method. If you need to understand how depreciation affects a larger financial picture, the calculation can be paired with operating forecasts or asset replacement planning.
Practical use in planning
A simple capex to depreciation estimate can help you see how a purchase affects future earnings, not just current cash. This is useful when you are deciding between two assets with different prices, lifespans, or resale values.
If you are comparing business spending categories, a Customer lifetime value calculator or Customer acquisition cost calculator may be useful in a broader budgeting model, but for capital assets the main question is still how much of the cost is consumed each period.
A good next step is to compare the annual depreciation amount against your expected revenue or operating budget so you can see whether the asset is affordable over its full life.
For more background, see Wikipedia.
Frequently asked questions
- What is a capex to depreciation calculator?
- It estimates how a capital purchase turns into annual depreciation expense. You give it the asset cost, salvage value, and useful life, and it spreads the depreciable amount across the life of the asset.
- What formula does it use?
- The common straight-line formula is depreciation per year = (asset cost − salvage value) ÷ useful life. In symbols, that is D = (C − S) / L. This is the simplest and most widely used planning method.
- Is capex the same as depreciation?
- No. Capex is the cash spent to buy or improve an asset. Depreciation is the accounting expense recognized over time as that asset is used.
- Why does salvage value matter?
- Salvage value is the amount you expect to recover at the end of the asset’s life. Subtracting it prevents you from depreciating value that is still expected to remain. If salvage value is zero, then the full cost is depreciated.
- Can I use this for tax depreciation?
- Sometimes, but not always. Tax rules may require a different method, life, or timing than straight-line depreciation. For tax filing, you should follow the rules that apply to your jurisdiction rather than relying only on a planning calculator.
- What if the asset has no salvage value?
- Then the depreciable base is simply the full asset cost. The annual depreciation is cost divided by useful life. That is a common assumption for many planning estimates.
- Does this calculator show book value too?
- The underlying method can be used to estimate book value after any number of years, but the main result is annual depreciation. If you want book value, subtract accumulated depreciation from the original cost.
About this article
Written by Yahav Atia, WSO – the digital agency (wso.co.il) that owns and founded this site, with the help of AI, and passed automated quality checks before publication. Numbers in the worked examples were computed in code, not estimated. This is general information, not financial or investment advice; check the figures against your own situation and official sources.