You move. Your wearable records it.
Walking, lifting, cycling, swimming. Activity and heart rate are measured; calorie expenditure is calculated using assumptions and algorithms.
A smarter way to use activity calories
Your wearable tracks the activity.
Calorie burn is an estimate.
Watches, fitness bands, rings and other wearables do an extraordinary job of tracking movement. But research shows their calories-burned estimates can be significantly inaccurate. When a calorie-counting app adds that estimate to your food allowance, shouldn't you have a say?
✓ More control for you and your personal trainer. · Built on research, not guesswork.
›› Your CalAdjust previewExample only
Your wearable reports
800 kcal burned
An estimate from a fitness tracker — not a direct measurement.
Choose the credit you want25%
Added to food allowance+200 kcal
Not added600 kcal
Example daily allowance
Based on a starting 1,800 kcal budget2,000 kcal
Based on a starting 1,800 kcal budget2,000 kcal
Move the slider. Your chosen credit, your numbers. This isn't a measure of true calorie burn.
✓ Keep the activity. Choose the credit.
Evidence-led. User-controlled.Independent scientific researchDesigned for people & personal trainersNutrition-app integrations in development
The real problem
The uncertainty doesn't stop at your wrist.
Wearables — including watches, fitness bands and rings — estimate energy expenditure using sensor data and algorithms. Some calorie-counting apps then turn those estimates into extra daily food allowance. That's where a measurement becomes a decision.
The calorie estimate isn't exact.
Studies repeatedly find much larger errors for estimated energy expenditure than for many heart-rate measurements. Errors can run in either direction.
Your food budget may increase.
Some calorie apps credit exercise expenditure towards your food allowance. What started as an estimate can become permission to eat more.
Fitness trackers accurately measure heart rate but not calories burned.
Stanford Medicine · Summary of its 2017 validation study · Read the research ↗CalAdjust doesn't tell you the “true” burn.
It gives you something much more useful in day-to-day food planning: a choice about how much of the estimate gets counted. The right setting depends on your goals, needs and training.
Don't just take our word for it
The science has been pointing to this problem for years.
Independent studies across different wearable devices and generations have repeatedly found that calorie estimation is harder than tracking heart rate or movement.
27–93%
Median energy-expenditure errors
Across seven wearables tested in a laboratory with 60 participants. Six of seven devices measured heart rate within 5% in the study's reported comparison.
View Stanford study ↗158
Publications, nine wearable brands
A broad review found no brand consistently accurate for energy expenditure. Only 9.2% of controlled-setting comparisons fell within ±3% of their reference.
Read the Fuller review ↗8 studies
Apple Watch energy-expenditure evidence
A review of 82 Apple Watch studies overall included eight on calorie expenditure (270 participants) and found errors were inconsistent and frequently large.
Read the 2026 review ↗What these figures do — and don't — mean: The Stanford range is the error observed across the devices tested in 2017, not a forecast for every modern wearable. Underestimation happens too. The evidence does not show that all wearables overestimate calories, or that any single CalAdjust credit setting is scientifically optimal. More research: 2022 systematic review and 2025 Apple Watch meta-analysis.
Meet CalAdjust
All your activity. A more intentional calorie allowance.
Stop treating every estimated calorie as a precise number. CalAdjust is being built to make the link between activity tracking and calorie counting more configurable.
Choose your own percentage
Credit all, some or none of eligible exercise calories to your food allowance, according to your own plan rather than a blanket rule.
Designed to be automatic
Less repeated mental maths, less manual diary editing. The goal is a consistent adjustment throughout the day where supported.
Keep your existing routine
Continue using your wearables and preferred food diary. CalAdjust is designed to complement your current tools, where integration is supported.
Built for better conversations
A practical new lever for you and your personal trainer.
Great coaching isn't about blindly trusting a number on a screen. It's about choosing a plan, tracking how things go, and adjusting to the individual.
✓Agree on how much estimated activity to credit towards daily food intake.
✓Make exercise-calorie allowances a deliberate choice, not an unnoticed default.
✓Keep the conversation focused on trends, consistency, recovery and sensible fuelling.
COACHING VIEW · CONCEPTYour client's choice
AActivity credit planChosen together, adjusted as needed25%credited
BHigher-fuel training dayA different setting, where appropriate75%credited
CFull activity creditWhen the plan calls for it100%credited
Illustrative coaching scenarios, not live client accounts or recommended percentages. A person's nutritional needs and training demands should guide decisions.
Your questions, answered
Clear thinking. No miracle claims.
What counts as a wearable?
Smartwatches, fitness bands, rings and other body-worn activity trackers. They may measure heart rate and movement and use those signals to estimate energy expenditure. CalAdjust's precise connections depend on the wearable, its data sources and supported nutrition-app integrations.
Are wearables always overestimating calories burned?
No. Published studies show both overestimation and underestimation. The problem is uncertainty, not a universal overestimate. That's why CalAdjust aims to offer user choice instead of automatically applying the same deduction to everybody.
What percentage should I choose?
There is no scientifically proven universal percentage. Your dietary goals, exercise volume, activity level and recovery needs matter. The interactive example on this page demonstrates the maths; it is not a recommendation to use 25%.
Does CalAdjust replace a food diary or personal trainer?
No. The aim is to work alongside the tools you use and the guidance you receive. It is a control over estimated activity calorie credit, not a new calorie-counting database or a substitute for professional advice.
Which calorie-counting apps work with CalAdjust?
We're developing and validating integrations. A working Nutracheck proof of concept has been tested; other platforms are under investigation. Not every integration is available, and compatibility shouldn't be assumed until confirmed. Sign up to express interest in early access.
Is CalAdjust available now? What does it cost?
CalAdjust is in development, with early access being planned. Public self-service signup and pricing are not yet available. The Sign up button lets you request information without creating an account. Existing pilot users can use Log in.
Move more. Guess less about what counts.
Research shows wearable calorie estimates aren't as precise as they look. CalAdjust is building a more considered way to turn activity into a food allowance — for individuals and the trainers supporting them.
In development. Availability varies by nutrition app. No claim of guaranteed weight loss.