Best BMI Tracker Apps for iPhone (2026): Track BMI Over Time

A BMI tracker app remembers your weigh-ins and shows where your BMI is heading, but most BMI apps are just calculators. You enter a height and a weight, get a number and a colored category, and that's it. That's fine if you want to know where you stand today. If you're losing or gaining weight, though, the more useful question is where the number is heading, and that needs an app that remembers.

A disclosure first. This comparison was written by the team that makes Periscope, a free weight tracker that shows BMI and is one of the apps below. We researched each app from its App Store listing and official website in October 2026. We didn't test every app hands-on for weeks, so where a listing doesn't say whether BMI is charted over time, we've written "Not stated". Prices and ratings are from the US App Store and will change. (For weight trackers judged on more than BMI, see our weight tracker apps compared.)

What's the difference between a BMI calculator and a BMI tracker?

A BMI calculator works out one number from one height and one weight. A BMI tracker stores your weigh-ins and shows how your BMI changes across weeks and months.

If you just want today's number, you don't need an app at all. Our BMI calculator does it in your browser. The formula is your weight in kilograms divided by your height in meters squared, or pounds divided by inches squared times 703, and the CDC's adult categories are:

A tracker earns its place when you're changing. It answers questions a single number can't: am I moving toward the range I'm aiming for, and how fast?

Why track BMI from a trend, not a single weigh-in?

Because for an adult, height stays the same, so BMI moves only when weight moves, and daily weight is noisy.

Here's an illustrative example. Take someone 170 cm (5 ft 7 in) tall. A BMI of 25 corresponds to about 72.3 kg (159 lb). Every 1 kg of body weight is worth about 0.35 BMI points at that height, and every 2 lb about 0.3. In one man weighed daily for more than 9,500 days, the typical day-to-day change was about 0.5% of body weight, and bigger swings after a salty meal or a hard workout are common. That means someone sitting near 25 could read "overweight" on Monday and "healthy weight" on Tuesday without any real change. Our explainer on why weight fluctuates daily covers those causes.

The fix is the same one that works for weight: calculate BMI from a smoothed trend weight rather than one morning's reading. Few apps say which weight they use; Periscope uses the trend weight. You can read more on the idea in what is trend weight.

How we compared

We looked for apps that show BMI for iPhone users and checked each one for:

1. Whether BMI is shown over time (a chart or history), or only as a current figure. We counted it only where the listing or site says so.
2. Where the BMI comes from: your typed weigh-ins, a smart scale, or a trend.
3. What else it tracks, since few people want BMI alone.
4. Price on the US App Store in October 2026.

What are the best BMI tracker apps for iPhone?

Periscope for BMI from a smoothed trend, Progress for BMI alongside body measurements, Weight Loss Simple Tracker for a plain BMI graph, and your scale's own app if you own a RENPHO or Greater Goods scale.

Several other weight trackers show a current BMI without saying whether they chart it: Happy Scale has a BMI calculator showing the weight ranges for each category, Weight Diary displays your BMI, and Noyoyo lists BMI among the things it tracks.

The apps, one by one

Periscope: best for BMI from a smoothed trend

Best for: people who want BMI as part of a calm, trend-based view of their weight.

Periscope is our app, and it's free with no in-app purchases. Add your height once and every weekly, monthly and yearly card in the Reports tab shows a BMI next to the smoothed trend line, your rate of change per week, your lowest weigh-in and an optional goal line. That BMI is read from your trend weight (a lag-corrected moving average) at the end of the period, so it doesn't jump around with each morning's water weight. When BMI isn't telling the whole story, progress photos help: attach them to weigh-ins and compare any two with a before/after slider. Apple Health sync brings in weights from a smart scale, widgets put the trend on your Home Screen, and weights and photos stay on your phone.

What to know: BMI lives in Reports; the Home chart shows your raw weigh-ins. Periscope doesn't track body fat or body measurements. It uses Sign in with Apple, and it's iPhone only, with no export or Apple Watch app. Widgets need iOS 17; the app runs on iOS 15.1 or later.

Price as of October 2026: free.

Progress: best for BMI with body measurements

Best for: people who'd rather watch waist and hip numbers alongside BMI.

Progress (now named "Body Measurements Tracker App" on the App Store) says more about BMI tracking than any other app here. Its listing says you can "calculate your BMI in seconds and watch how it changes over time," and describes itself as "a full BMI calculator and tracker." It also tracks 17 body measurements plus up to 10 custom ones, body fat, and front, side and back photos. Apple Health sync works both ways, and data stays on your device and your own iCloud, per the listing. Rating: 4.63 from 9,358 as of October 2026.

What to know: progress photos and unlimited measurement areas are Pro features, and it needs iOS 18. A smoothed trend isn't mentioned.

Price as of October 2026: free; Pro $3.99 to $5.99 a month, $11.99 to $19.99 a year, or $29.99 lifetime.

Weight Loss Simple Tracker: best simple BMI graph

Best for: a plain weight log with a BMI chart and not much else.

This app (developer STTIR) calculates BMI automatically from your entries and charts it next to weight, body fat, steps and muscle mass. An avatar changes with your BMI level, which some people will find motivating and others won't. It has reminders, notes and a passcode lock. Rating: 4.70 from 2,192.

What to know: the free version has ads, and Apple Health weight sync and backup are Premium features.

Price as of October 2026: free with ads; Premium $3.99 a month or $29.99 a year.

RENPHO Health and Weight Gurus: best if you own the scale

Best for: people with a RENPHO or Greater Goods smart scale.

A body-composition scale records BMI with every weigh-in, so its app becomes a BMI tracker by default. RENPHO Health tracks BMI, body fat, body water, muscle, bone mass and more, supports multiple profiles, and its listing says it syncs BMI to Apple Health. It's free and cloud-based. Rating: 4.71 from 8,990.

Weight Gurus shows BMI among more than a dozen metrics from Greater Goods scales, works offline, and offers cloud backup with a free account and CSV export. Rating: 4.41 from 1,027.

What to know: both are built around their own hardware, and neither describes a smoothed trend.

Price as of October 2026: both free, no in-app purchases.

Apple Health: the place BMI can collect

Best for: keeping BMI from several sources in one place.

Apple Health has a Body Mass Index data type that other apps and scales can write to, and it charts whatever arrives. If your scale or app writes BMI there, you have a BMI history without installing anything else. We couldn't confirm from Apple's own documentation whether Health calculates BMI for you from your weight and height, so check yours under Body Measurements. Our guide to Apple Health weight tracking covers permissions and duplicate entries.

Price: free.

A one-off calculator: BMI Calculator – Weight Loss

Best for: checking BMI occasionally, including for children 7 and up.

This is the most-rated calculator we found (4.52 from 29,209). It offers WHO or German Nutrition Society classifications, works offline and has an adults-only mode. Its listing doesn't describe a history or chart, so we treat it as a calculator.

Price as of October 2026: free; $2.99 to remove ads.

Which BMI tracker app should you pick?

If you want BMI as part of a simple weight tracker, we'd pick Periscope: it's free, it calculates BMI from your trend rather than one morning's reading, and it adds progress photos, widgets and Apple Health sync, with your weights kept on your phone. Progress is the stronger choice if you want waist, hips and other measurements next to BMI. By need:

• You just want today's number: our BMI calculator or a one-off calculator app.
• You want BMI that doesn't jump around with water weight: Periscope, which uses your trend weight.
• You want a dedicated BMI chart and body measurements: Progress.
• You want a simple BMI graph: Weight Loss Simple Tracker.
• You own a smart scale: its own app, writing to Apple Health, with Periscope on top if you want BMI from a smoothed trend.

Whichever you choose, keep BMI in proportion. The CDC describes it as a screening measure that doesn't distinguish between fat, muscle and bone, and NICE recommends adding waist-to-height ratio, keeping your waist under half your height. Our article on whether BMI is accurate explains where it works and where it misleads. If tracking numbers about your body makes you anxious, or you have a history of disordered eating, it's fine to step back; the National Eating Disorders Association can help.

Sources

1. CDC. Adult BMI Categories
2. CDC. About Body Mass Index (BMI)
3. Day-to-day weight variability in one man over 9,521 days (PubMed)
4. NICE. Overweight and obesity management (NG246): identifying and assessing overweight, obesity and central adiposity
5. Periscope on the App Store
6. Progress (Body Measurements Tracker App) on the App Store
7. Weight Loss Simple Tracker on the App Store
8. RENPHO Health on the App Store
9. Weight Gurus on the App Store
10. Monitor Your Weight on the App Store
11. BMI Calculator – Weight Loss on the App Store
12. Happy Scale on the App Store
13. Weight Diary on the App Store
14. Noyoyo on the App Store