Asset Depreciation Calculator Guide

Depreciation is how businesses spread the cost of a fixed asset over its useful life, rather than recording the whole expense in the year of purchase. For IT assets such as laptops, servers, and network hardware, depreciation helps you match the cost of the equipment to the periods that benefit from using it. This guide explains straight-line depreciation, the most common method for IT equipment, with a worked example and a free calculator you can use right now.

How straight-line depreciation works

Straight-line depreciation is the simplest method. You take the purchase cost of the asset, subtract its expected residual value at the end of its useful life, and divide the result by the number of years you expect to use it. The same amount is depreciated each year.

The formula is:

Annual depreciation = (Cost – Residual value) / Useful life in years

A worked example

Imagine your business buys a server for £4,800. You expect to use it for 4 years, after which its resale value will be around £400.

• Cost: £4,800
• Residual value: £400
• Useful life: 4 years
• Annual depreciation: (£4,800 – £400) / 4 = £1,100 per year

Each year, you record £1,100 of depreciation. After 4 years, the accumulated depreciation is £4,400, and the net book value of the server is £400, matching its expected residual value.

Free asset depreciation calculator

Enter the purchase cost, residual value, and useful life to calculate annual and monthly depreciation. All figures are in pounds sterling.

This calculator is a guide for straight-line depreciation. It does not constitute accounting or tax advice. Always confirm your depreciation policy with your accountant or finance team.

UK depreciation rules: Capital Allowances and the AIA

Depreciation in your accounts is an accounting concept. For tax purposes, HMRC uses a different system called Capital Allowances. Capital Allowances let businesses deduct the cost of qualifying capital equipment from their taxable profits, instead of deducting depreciation.

The two concepts that matter most for IT assets are:

• Annual Investment Allowance (AIA) – businesses can deduct the full cost of qualifying plant and machinery, including most IT equipment, up to a set annual limit in the year of purchase. The AIA limit is £1 million. Most SME IT spend falls well within this, so laptops, servers, and network hardware are typically written off fully in year one for tax purposes.
• Writing Down Allowance (WDA) – where spending exceeds the AIA limit, or the asset does not qualify for the AIA, the cost is deducted at a percentage each year instead. Most plant and machinery falls in the main rate pool at 18% on a reducing-balance basis, while some assets, including longer-life equipment, fall in the special rate pool at 6%.

Most IT assets, such as computers, servers, and peripherals, qualify for the AIA. Software is treated differently, as it is usually an intangible asset or a revenue expense depending on how it is acquired. Always check the current position with HMRC guidance or your accountant, as rates and limits can change.

Because accounting depreciation is added back for tax and replaced with Capital Allowances, businesses often keep two views of an asset: the accounting net book value and the tax written-down value. Tracking both by hand across a spreadsheet is where errors creep in.

How AssetGraph tracks asset values over time

AssetGraph keeps your asset register, including purchase date and cost, in one place and updates it as devices are discovered, reassigned, and retired. Because the register is fed passively from Microsoft Graph, Intune, Jamf Pro, network discovery, cloud provider APIs, and procurement systems, the cost and lifecycle data stays current without manual entry.

• Live asset values – purchase cost, purchase date, and status are maintained as part of the canonical asset record, so depreciation calculations work from the same source as your discovery data.
• Lifecycle tracking – when a device is disposed of or retired, the status and date are recorded with a timestamped audit trail, so you know exactly when to stop depreciating it.
• Reconciliation – the same device appearing in procurement, Intune, and your MDM is matched and shown once, so you do not double-count or lose assets between systems.
• Audit evidence – every state change is logged, giving you the records an auditor or accountant needs without rebuilding them from scattered spreadsheets.

AssetGraph is designed to support ISO 27001, SOC 2, and ITIL workflows. All traffic is encrypted in transit over HTTPS, API credentials are stored server-side and never in the browser, read-only connector scopes are used where supported by the API, and your data is hosted in the EU on Supabase in eu-west-1. AssetGraph is not itself certified.

Start tracking asset values with a free trial

Use the calculator above to work out depreciation for a single asset. When you want to track cost, status, and lifecycle across your whole estate without manual spreadsheets, start a 7-day free trial of AssetGraph. No card is needed to sign up, and you can pay by direct debit.

Pricing is simple: Starter at £29/mo, Professional at £99/mo, and Enterprise at £299/mo. Pay annually and get 50% off. Prices exclude VAT.

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Depreciation is only as accurate as the asset data behind it. A live register that updates itself means your values stay correct from purchase to disposal.