A macro tracking app splits the daily target into protein, carbohydrate and fat and logs each food against it. Because the macro breakdown is usually the paid feature, a macro tracking app is rarely free for the thing you actually want, so the honest question is what the upgrade costs, with the free macro split arithmetic on this site beside it.
Macros are usually the paid tier
Most tracking apps count calories free and put the macro split behind a subscription, so a macro tracking app that shows protein, carbohydrate and fat at no cost is rarer than it looks. Read what the free tier includes before committing, because on many apps the macro breakdown, the very thing a macro tracking app is for, is the paywalled feature.
What the plan costs
When macros are behind the paid tier, the number that matters is the annual price, not the intro month, because you track the same split all year. The app price record on this site quotes those figures from each app's own page, so you can weigh the convenience against the cost before you rely on a free tier that limits macros.
The split itself is free
Whatever app you use, the macro target is free arithmetic: the macro calculator on this site produces your protein, carbohydrate and fat split from bodyweight and goal. A macro tracking app charges to make daily logging against that split convenient, not to work it out, so knowing your numbers never needs a subscription.
Questions people ask about macro tracking app
Is there a free macro tracking app?
Some apps count calories free but put the macro split behind a paid tier, so check what the free version includes; the macro target itself is free arithmetic you can get without any app.
What does a macro tracking app cost?
A subscription once macros are behind the paywall, and the annual price matters more than the intro month; the price record here quotes each app's own figure.
Do I need an app to track macros?
No. The macro calculator here gives you the split for free; an app only makes daily logging against it convenient, which is what the subscription buys.