Most apps hand you the brochure figure. A calorie burn worked out on an average person, in perfect conditions, and never checked against you again. Kriterion is the trip computer. Your number, measured from your own food log and weight trend, with the margin printed next to it so you know how much to trust it.
Government lab data at the core. Everyday foods from the UK’s and the USDA’s lab-analysed databases. American brands from the USDA’s own records. UK and Irish chain menus from the figures the chains publish. European packaged brands through Open Food Facts. Every entry is badged with where its numbers came from, so you always know which ones were measured.
Logging is free forever. No adverts, no account, no fortnight before it takes your history hostage.
I have spent years researching this, working in the fitness industry and coaching other people through it. Then came a new baby, a job with a lot less movement in it, a new area, and a man in the mirror I thought I knew exactly how to coach and had not been helping.
So I went back to the research to find out how much of what I had been taught had moved on. A fair amount of it had. Then I spent a considerable amount of time and money on computer modelling, running the formulas against simulated bodies with known answers, so I could find out where they were wrong rather than assume they were right.
Then I started again from the ground up for women, because female physiology is not a correction factor you apply to a man's. Kriterion knows where you are in your cycle and expects the water that comes with it, so it does not read it as fat and does not cut your calories over it. It knows creatine holds water too, and treats that as the good sign it is. I have not found another tracker that handles either of them properly. Most cannot tell water from fat at all, so they panic, and then you do.
I think this is the most accurate tracker you can get. I would think that, though. Which is why the margin is printed next to the number, and why the app grades its own past predictions against what your scale actually did and shows you the result. You do not have to take my word for any of it. You can watch it check itself on your own data.
Josh, founder
Most trackers either guess your calorie burn from a formula and present the guess as fact, or bury the truth under an interface that feels like doing your taxes. Kriterion measures instead of guessing, then explains it the way a person would.
If you have ever eaten exactly what an app told you to and watched the scale refuse to move, you were not doing it wrong. You were following a number a textbook equation guessed on day one and never checked again.
Most apps congratulate you for opening them. It feels good for about a week, and then it feels like nothing, because praise that costs nothing is worth nothing.
The dangerous moment was never the missed week. It is opening the app afterwards and finding a broken streak and a wall of red waiting to tell you off.
Every number in here can be traced to something: a lab measurement, a published study, or your own logged data. Where the evidence is thin, the app says so instead of rounding up to confidence, and there is a reference library you can read to check the reasoning for yourself.
Already using something else? These go feature by feature, including what the other app does well.
An app that talks to you every day should talk to you the way you actually respond to. Kriterion never changes the facts to suit the tone.
“12 days away is a real reset. Half volume today, full effort.
Earn the rest back.”
“12 days since your last session. I've trimmed today's volume so you rebuild without overdoing it.”
“12 days is a long stretch, and that's okay.
Here's a soft restart, well under your usual
volume.”
A colour here is not an accent on a button. It repaints the ground the whole app sits on, in light and in dark, out as far as the widget on your home screen. What it never touches is a single figure on the screen.
SteelMidnight
Dusk
Iris
EmberTwo figures, and only one of them is about you.
Photograph the nutrition panel and the numbers come straight off it.
An actual capture, not a mock-up, picking up in Recent Foods: tap one and it logs again immediately, with a toast to confirm it and the day's totals updating underneath.
Kriterion checks your readiness before it suggests a session, keeps the numbers that actually drive progress, and notices the things you would rather it noticed for you. Connect a watch or ring and readiness reads your HRV and resting heart rate every morning.
Both figures are drawn from the same logged week. The map follows the anatomy you set in your profile, and every muscle it names is one you can tap to see what trained it.
The timer keeps running with the screen off and your phone in your pocket, and on Premium every interval is called out loud.
Most fitness apps bolt the menstrual cycle on as a separate calendar.
“Oestrogen hits its highest point of the cycle and body temperature begins to rise. Strength often follows, though ligaments are looser than usual, so form is worth protecting.”
Cycle phases are estimated from the dates you enter and are not a contraceptive method and not a fertility test. Kriterion is a wellness tracker, not a medical device. If your cycle changes unexpectedly, speak to a doctor or pharmacist.
Am I actually getting anywhere.
Most apps ask you to take the science on faith and never show you any.
“Two days can carry an identical 150g of protein and be nothing alike… Kriterion uses the higher figure for everyone rather than branching on age: for a younger user it is a slightly conservative target rather than a wrong one.”
Read some now: protein timing, why a calorie estimate needs an error bar, how far to trust your watch, why the scale jumps after a salty weekend, or the whole library.
Plenty of trackers give you a fortnight and then take your own history hostage. Kriterion does not. Logging is the part you do every day, so logging is the part that stays free, permanently and without a cap.
| Free, always | Premium | |
|---|---|---|
| Food logging | Unlimited by hand or search, ten barcode scans a day | Unlimited, by hand, search or barcode |
| Your history | Kept in full, never truncated | Kept in full, never truncated |
| Food database | Every food source, nothing held back: UK government data (CoFID), USDA, Open Food Facts, 30+ UK and Irish chains, supermarket own-brand and supplements | Every food source, nothing held back |
| Label and scale photos | Unlimited, read on your device | Unlimited, read on your device |
| Barcode scans | Ten a day | Unlimited |
| Where your calorie target comes from | A formula, worked from your own body rather than your results, using your lean mass where you have measured it | Measured from your own results rather than assumed from a table |
| Does it change as you log? | It follows your weight and body composition as those change, but not what your results say | Yes. Every day you log moves it |
| How settled the number is | Nothing to show. A formula has no measured spread | Shown, so you know whether to plan a week around it or wait |
| Checks its own past predictions | Not offered | Yes, within the first few weeks, and it sharpens every day after |
| Routines | Two you build yourself, plus every standard programme | Unlimited routines |
| Your burn rate over time | Not offered | Charted week by week, with its margin drawn around it and the textbook formula plotted alongside, so you can watch the two separate |
| Where your calories actually went | Not offered | Eaten against burned, day by day, with the running average and every day you were over or under marked |
| How steady your logging is | Not offered | Rated, because an unsteady log is the main reason a target moves around and you should know which it is |
| Micronutrients over time | Today only | Averaged across your logged days, against your region’s own reference values, with the share of them actually measured shown |
| Macro balance | Today’s totals | Protein, carbs, fat, fibre and sugar headroom on one shape, so a lopsided week is obvious at a glance |
| Strength progress and weekly review | Not offered | Lift by lift over time, plus a weekly check-in |
| Body measurements and progress photos | Log them, free | The trend chart, and photos compared side by side |
| Recipes, supplements and nutrient trends | Build and save up to ten recipes | Unlimited recipes, recipe import, supplement insights and nutrient trends |
| Training extras | Supersets and circuits | Plans written for you, specialist methods, run coaching, coach tone, 1RM and DOTS |
The split is deliberate, and it is the same line in both directions. Free gives you the number a formula can work out about a body like yours. Premium gives you the number your own data works out about you, and keeps correcting it. That second one is worth nothing until you have logged enough for the maths to mean something, so the logging can hardly be the thing you pay for. Kriterion does not go quiet while it waits, either. From your first couple of weeks it shows what your own data is starting to say, side by side with the target, and how close you are to it taking over.
Your weight, your food, your cycle. It is the most sensitive thing an app can hold, and in this industry it is routinely treated as inventory. Here is exactly how Kriterion treats it instead, including the parts that aren't purely on-device.
Every app on earth claims to suit everyone. Here is where this one genuinely does not, so you can find that out now rather than three weeks in.
If none of that put you off, it was probably built for you.
Everything on this page has the long version behind it. These are the questions we get asked most, answered properly.
Kriterion is full of numbers, and it works hard to make them true ones. But a figure on a screen is only useful if it answers to the person reading it. Yours adapt to what your body actually does, they tell you how far to trust them, and they change tone when you ask. That is the whole idea: the standard is yours to set.
Join the list and you get the founding offer: a lower price, locked in for as long as you stay subscribed. It is capped at the first 1,000 subscribers or 90 days from launch, whichever comes first, and it will not be extended. A confirmation now, then one email on the day it launches. Not a newsletter, not a drip sequence.
It is a wellness and training tracker. It is not a medical device, and it does not diagnose, treat, cure or prevent any condition. Everything it shows you, from calorie and macro targets, your estimated burn rate, readiness, body-composition figures, cycle phases and anything in the reference library, is general information to help you make your own decisions, not medical, nutritional or clinical advice, and not a substitute for a qualified professional who knows your history.
Talk to your GP, a registered dietitian or another qualified clinician before making significant changes to how you eat or train, and particularly if you are pregnant or breastfeeding, managing a health condition, taking medication, or have a history of disordered eating. Estimates are estimates: they are derived from what you log, and they carry real uncertainty, which is why Kriterion shows you that uncertainty rather than hiding it.