Most business cases for IT asset disposition are built on resale value. The provider supplies an estimate, the estimate becomes the headline, and the programme gets approved on the promise of a cheque. Then the cheque arrives smaller than expected, and the programme is quietly reclassified as a cost.
That pattern is not usually anyone's fault. Resale value is genuine, but it falls steeply with age, it moves with a market nobody controls, and estimates tend to be taken from the newest equipment in the estate and applied to all of it. A case resting on that single input is a bet on the used hardware market, presented as a saving.
This calculator builds the case the other way round.
It starts with cost avoidance, the part measurable from inside your own organisation and indifferent to any market: floor space occupied by retired equipment, internal handling time spread thinly across several people, and disposal invoices scattered across cost centres. It then adds the programme's own costs, including the two most business cases leave out, programme management time and the one off setup cost. A case that omits them gets corrected by the first finance reviewer who reads it.
Resale value comes next, handled with more care than any other input. Residual percentage is entered per category and matched to age at retirement, because a three year old laptop has a market and a six year old one largely does not. Dwell time is an input too, because every month equipment waits in storage it moves further down the value curve. That mechanism, rather than harder negotiation, is where most of a managed programme's uplift actually comes from.
Then the calculator stress tests it. A sensitivity table reruns the case at 100, 75, 50, 25 and 0 per cent of estimated resale. The right hand column is the one to lead with. If the case is positive with resale set to zero, the programme is justified before a single device is sold, and resale becomes upside rather than the premise. In the illustrative worked example, the annual improvement falls from £51,128 at full resale to £17,696 at zero, and remains positive throughout.
Two things are deliberately kept out of the headline.
The refresh cycle lever is usually the largest figure in the workbook. In the example, moving a 1,600 device fleet from a three year to a four year cycle avoids around £113,000 of replacement spend a year, more than twice the disposal case. It is shown separately because it is a different decision, owned by different people, and a disposal case that quietly absorbs it gets taken apart the moment someone notices. It also carries the workbook's one carbon figure, which belongs inside your inventory under Scope 3 Category 1, unlike avoided emissions from equipment reused by somebody else.
Risk reduction is shown and excluded by default, behind a switch. Every input is a judgement, and the guide argues against the most common mistake here: applying a published average data breach cost to a disposal case. Those averages describe enterprise breaches of every kind, including ransomware and prolonged compromise, and are a poor proxy for a single mislaid laptop. A case that only works once risk is included is a weak case. One that works without it, with risk shown alongside as exposure removed, is a strong one.
The workbook has nine tabs: Summary, Inputs, Estate, Residual, Scenarios, Refresh, Risk and Assumptions, plus a read me. Every default is illustrative and highlighted for replacement, and the Assumptions tab records the source and reasoning behind each input, because a finance reviewer will ask.
The 20 page companion guide explains every input, where to find it, and how to present the result. Three appendices: a data gathering plan listing who holds each figure, a one page summary structure for the finance paper, and a 14 point readiness checklist.
All figures in the worked example are illustrative. Replace every one with your own before the case is shared.