Decay vs Appreciation

What is it worth now, and what would the money have been worth?

Most things you buy start losing value the moment you own them. The money you could have invested instead does the opposite. This tool draws both lines on one chart - what the thing is still worth, and what the money would have grown to - and states the gap between them. Both sides are measured in today's money, deflated by the same inflation, because comparing a resale price to an investment balance any other way flatters one of them. It is not an argument against buying things. Set the decay rate below zero and it will show you an object that beats the market, because some do.

The purchase

These figures are a worked example - a new car, bought once, held ten years. Replace them with your own. The tool does not care whether the thing is a car, a kitchen or a guitar; it only needs what it cost, how often you buy it, and how fast it loses value.

What it cost The price you paid, or pay each time if this is a repeat purchase. Use the real out-the-door figure rather than the sticker - the tool measures what actually left your account. How often A single purchase decays from its own date. A repeat purchase builds a pile of objects of different ages, each decaying from the day you bought it - which is why a habit and a one-off with the same total look nothing alike on the chart. Over how many years The free version answers up to 20 years. Enter more than that and it will show you 20 and say so rather than quietly cutting the answer short; Pro runs to 50.

How fast it loses value

There are two ways to answer this and the second one is easier to be honest about. Either state a rate, or say what you think the thing will fetch at some point and let the tool work out the rate that implies. Nobody knows their own depreciation rate; plenty of people know roughly what their car is worth.

Which way Both routes end in the same place - a percentage a year - and the tool always shows you which rate it used, so the second route is a way of arriving at a number rather than a way of avoiding one. Value lost each year (%) 15% is the figure usually quoted for a new car; it is a placeholder, not a measurement, and this plugin has no resale-value feed. A NEGATIVE number is allowed and means the thing gains value - enter -3 for a house and the tool will happily show you an object that outruns the market, or does not.

The money, if you had invested it instead

Return above inflation (% a year) A REAL return - what the money grows by after inflation has been taken out. 7% is the house assumption across these tools and it is an assumption, not a forecast. Enter a lower one if you think it is optimistic; the gap narrows and the tool will not argue with you. Inflation (% a year) Applied to BOTH sides, which is the point. A resale price is a number in the money of that future day, exactly like an investment balance, so deflating one and not the other would overstate the gap in the flattering direction. This tool deflates them together. Annual fees on the investment (%) Pro. Left at zero, which is the honest default for someone who has not chosen a fund yet - and it is the setting that flatters the investing side, so the free tool is not quietly tilting the comparison. It never falls below (% of what you paid) Pro, and it travels with the long horizon for a reason: pure exponential decay says a $40,000 car is worth thirteen cents after fifty years. The floor is what stops a fifty-year answer printing an absurdity, so the two are one purchase rather than two.

The free version draws both curves in full, up to 20 years, and never clamps the answer inside that range: the gap, the half-life, and what a year of owning the thing costs. Pro runs to 50 years, adds the residual floor that keeps a long horizon honest, shows every horizon at once, works out the rate the object would have to appreciate at to have beaten the market, pins several purchases side by side, and adds image and CSV export.
The shareable link is free, for everyone, always. Pro is a separate one-time purchase - if you already subscribe to DCA Simulator Pro, this is not included in it. Worth knowing before you click, rather than at the checkout.

Educational content only - not financial advice. Every headline figure is in today's money: both the thing and the money are deflated by the same inflation rate, because that is the only way the two are comparable. Decay is modelled as a constant annual rate, which real objects do not obey - most lose value fastest at the start - so treat the curve as the shape of the thing rather than a valuation. The market return is an assumption you chose, not a forecast, and no investment returns a fixed rate every year. The tool ignores running costs, insurance, maintenance, tax, and the use you actually got out of the thing, which is usually the entire reason for buying it. Run your own numbers.