You sign in on Tesla’s page — never a password here
Delete your data in one click
What you get
What we can and can’t touch
It can wake your car — and that’s all
To read a sleeping
car we have to wake it, and Tesla bundles wake in with other commands. We call exactly two
things: wake, and read. On cars from late 2023 on, unlocking or driving needs a virtual key you
would have to add in your Tesla app — we never ask for one.
It never sees your password
You sign in on Tesla’s own page.
Never type your Tesla password into a third-party site, including this one. We will never ask.
It doesn’t keep the keys
We read once and throw the token
away. No stored refresh token, so a breach here reaches nobody’s vehicle.
It doesn’t know who you are
No account, no email, no VIN,
no name — just a random id in your own browser.
What counts as normal Tesla battery degradation
Every pack loses capacity. The real question is whether yours is
losing it faster than it should:
Odometer
Typical remaining capacity
What it means
0–25k mi
95–98%
The fast early drop. Alarming to watch, completely normal.
25k–50k mi
92–96%
The curve is already flattening out.
50k–100k mi
88–93%
Slow, steady. Most cars live here.
100k–150k mi
85–90%
Still far above the warranty floor.
150k mi+
80–88%
Tesla's 8-year warranty floor is 70%.
Commonly observed across large owner-reported
datasets — context, not a guarantee. Your own result is measured from your car.
How to check your Tesla’s battery health
You authorise on Tesla’s own login page. Your credentials are typed at auth.tesla.com,
never here. Tesla hands this site a short-lived read token.
We wake the car if it is asleep, then read it once. Two calls, no more: a wake, and one data
request for charge level, rated range, odometer and vehicle configuration.
We scale that range to a full charge. Rated range ÷ charge level × 100 = your
range at 100%. A car showing 239 miles at 72% has 332 miles at 100%.
We divide that by what your exact build shipped with. 332 against the 353-mile EPA rating of
a 2021 Model 3 Long Range is 94.1% of original capacity — 5.9% degradation.
We drop the token and keep only the numbers, filed under a random id in your own browser.
Every figure on your result is shown with this same working,
using your own numbers rather than the example ones.
Every number, and where it comes from
Number
How it is worked out
Where it comes from
Range at 100%
rated range ÷ charge level × 100
Your car, on this read. Tesla’s rated range already tracks the pack’s current capacity, which is what makes it usable here.
Original EPA rating
Looked up by model, model year and trim — and wheel size where that changes the rating
Tesla’s published EPA figures. The model year comes from position 10 of your VIN, read in memory and never stored.
Health %
range at 100% ÷ EPA rating × 100
Derived from the two rows above. Nothing else feeds into it.
Degradation %
100 − health
Derived.
Loss per 10k mi
degradation ÷ odometer × 10,000
Derived. Withheld under 2,000 miles, where it is meaningless.
Projected at 100k / 200k
A square-root curve fitted through your one measured point
Modelled, not measured. Degradation is sub-linear, so a straight line is far too pessimistic at high mileage.
Your percentile
Your health against every other car of the same model tested here
This site’s own database — a small, self-selected pool, not the national fleet. It appears only once three or more comparable cars exist.
Typical band
The shaded band on your chart, and the table above
Large owner-reported datasets. Context to read your number against — it never goes into the number itself.
When we refuse to give you a number. If we hold no
verified factory rating for your exact configuration, or your car reports more range at 100% than our
baseline says it left the factory with, you get the measured figures and no degradation percentage at
all. A wrong baseline either invents degradation that is not there or prints a flattering 0.0% —
both are worse than an honest blank.
What moves the reading. It is one snapshot, taken whenever you run it.
Rated range is least accurate at a low state of charge; a cold pack holds back a buffer that returns as
it warms; LFP packs report capacity differently and wander more between reads. Your result flags each of
these when it applies. One point is a rough figure — the trend across several reads is the real
signal, which is why the test is repeatable and why we offer to tell you when your number moves.
What this is not. Not a service diagnostic. It cannot see cell balance,
module faults or your 12V battery, and it is no substitute for Tesla service if something looks wrong.
Battery test questions
How do you work out the battery health percentage?
From two numbers your car reports: its charge level right now, and the rated range showing on its screen right now. Rated range ÷ charge level gives your range at 100%. That divided by the EPA rated range your exact model, year and trim shipped with is your remaining capacity. Worked example: 239 miles showing at 72% charge is 332 miles at 100%; against the 353-mile EPA figure for a 2021 Model 3 Long Range, that is 94.1% health — 5.9% degradation. Neither input is estimated; both come from your own car in a single read.
How much Tesla battery degradation is normal?
Most packs lose their first few percent quickly, then flatten out. Roughly 5% in the first 25,000–50,000 miles is ordinary, and the curve bends: the second 5% takes far longer than the first. Tesla's own warranty standard is that the pack retains at least 70% capacity over 8 years, so anything comfortably above that at normal mileage is not a problem.
Does this need my Tesla password?
No, and you should never give your Tesla password to any third-party site. You sign in on Tesla's own login page, and Tesla hands us a read-only token. We never see your credentials.
Can this site unlock, drive, or locate my car?
No. We ask Tesla for two permissions: read access to vehicle information, and the command permission — which we use for exactly one thing, waking a sleeping car so that it can answer. Wake and read are the only two calls this site ever makes. We never request location access, and unlocking or driving a modern Tesla additionally needs a virtual key physically added in your Tesla app, which we never ask for and could not use.
Why does it need to wake my car?
A sleeping Tesla will not answer a data request — it returns nothing at all. Waking is the only way to read a car that has dozed off, and Tesla files wake under the same command permission as everything else, so requesting it is unavoidable. If the wake fails we tell you to open your Tesla app and try again rather than retrying at you.
Do you store my Tesla login?
No. We read the car once, compute the numbers, and discard the token. There is no stored refresh token, so this site cannot reach your car again until you choose to reconnect.
Why is my range lower than the EPA number even at 100%?
Two different things get confused here. The rated range on your screen is a fixed EPA figure multiplied by your pack's current capacity — it drops as the pack ages. Your actual miles also depend on speed, temperature, terrain and tyres, which is why a healthy pack can still under-deliver on a cold motorway run.
Is a lower number worth worrying about?
Usually not on its own. Degradation is gradual and mostly cosmetic until it affects your daily use. A sudden step change, or a figure far below other cars of the same age and mileage, is the thing worth investigating — which is exactly what the percentile here is for.
Independent fan project.
Not affiliated with, endorsed by, or connected to Tesla, Inc. Figures are estimates derived from your
vehicle's own reported data and are not a substitute for a service diagnosis.
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