Kelley Blue Book has been setting the price reference for used cars for decades. If someone quotes you “Blue Book value,” they mean a real, well-constructed number.
But a Blue Book value is a today number. The question that actually matters when you're buying is rarely “what is this worth” — it's “what will this be worth when I sell it, and did I make the right call.”
What KBB does well
KBB gives you trim-level pricing, mileage adjustments, options values, and a trade-in range. It's the reference buyers and dealers both agree on, and it's transparent about how condition and mileage move the number.
If you want to know what your specific car is worth today, KBB is excellent and you should use it.
KBB also runs a separate 5-Year Cost to Own calculator with depreciation projections for new vehicles. What follows is about its valuation and trade-in tool — the one most people mean by “Blue Book value.”
The question a valuation doesn't answer
Here's the actual buying decision: two cars, both priced about the same today. One holds 60% of its value in five years. One holds 35%.
KBB's valuation tool can tell you what each is worth now. A today price can't tell you which one you'll regret. That's not a flaw in the valuation — it answers a different question. It's a gap.
Depreciation is typically the single largest cost of owning a car. Often larger than fuel, insurance, and maintenance combined. And it's the cost that happens whether you look at it or not. A tool that only shows you today's price is showing you the cheapest part of the decision.
What Predictye shows instead
For each model, Predictye gives you:
The depreciation curve. Year-by-year projected value, so you can see where the steep drop happens. Almost all cars lose their fastest value in year one and two, then flatten. Knowing that changes when you sell.
Annual retention. What fraction of value survives each year, and what survives five years. That's the number to compare between options.
Running cost, alongside value loss. Fuel, insurance, maintenance, and registration — next to the money you lose to depreciation. Added together, that's the true annual cost of the car.
When to sell. Based on where the depreciation curve bends.
Used car or new, the real comparison
The most useful thing depreciation data gives you is the new-versus-used decision, which people get wrong constantly.
A three-year-old car still under warranty may have already absorbed the steepest part of its depreciation. It has a known service history, known remaining life, and immediate resale value. It's frequently the better buy than a new one, and you'll only see that if someone shows you both curves.
What Predictye doesn't do
We're not a substitute for KBB. We don't do auction data, we don't price specific vehicles, and we can't account for accident history, aftermarket modifications, or a title issue. If you need a number for a specific car with specific miles and options, KBB is the right call.
We're forecasting the model, not pricing your individual vehicle.
Frequently asked questions
Is KBB more accurate than Predictye?
For valuing a specific vehicle today, yes — they have auction and dealer transaction data we don't. For forecasting where that model goes in five years, that's the question we exist to answer.
How accurate is car depreciation forecasting?
Car depreciation is unusually predictable compared to most asset classes, because manufacturers refresh models on a known cycle and buyers have strong brand preferences. That's why the curves are more reliable here than for most things. Still an estimate, not a guarantee.
Can I use KBB and Predictye together?
Yes. KBB's valuation tool for today's value, Predictye for the trajectory. Buy with KBB, sell with Predictye.
Is Predictye free?
Yes. No account needed.