Spren App vs. Corpus (2026): Cost, Accuracy Claims and What You Get

The short answer: Spren is an iPhone app that estimates body fat, fat mass, lean mass and resting metabolic rate from a full-body selfie. It’s free to download, with in-app purchases listed from $10.49 to $119.99 on the US App Store. Spren says its results are comparable to DEXA scans; independent research on photo apps finds good accuracy for groups but weaker accuracy for one person. If you want a weekly trend with a photo record, Corpus is the alternative built for that, with no published accuracy data.

What the Spren app does

Spren asks you to “simply snap a full body selfie on your smartphone.” According to its App Store listing, you get “a multi-page PDF report” with body fat %, fat mass, lean mass, A/G fat ratio and resting metabolic rate.

Beyond the scan, Spren’s website describes:

• Nutrition targets that Spren says are based on “your body composition, age, ethnicity, activity level, recovery,” and more.
• AI coaching, which Spren says is “there 24/7 to keep you on track.”
• HRV scans. Spren’s release notes describe its Scan Essentials tier as “unlimited Body and HRV scans, plus metrics, for a third of the full Pro tier.”

If you searched “spren app android”: the listing says Spren is “Only for iPhone.” The “android fat” in its reports is a fat region, which Spren defines as “body fat around the trunk and upper body.”

What Spren costs

Spren is free to download, and the plans are in-app purchases. The US App Store listing shows these, exactly as listed:

• Annual: $69.99 and $119.99
• Monthly: $14.99 and $19.99
• Quarterly: $59.99
• Scan Essentials: $10.49 and $38.99

The listing doesn’t say which tier each annual or monthly price belongs to, so check the in-app paywall before you subscribe. Prices change; these were checked in October 2026.

What Spren’s accuracy claims rest on

Spren’s App Store listing says its “results are comparable to DEXA scans” and that “the science behind the imaging algorithm has been validated by several independent peer-reviewed studies.” Those are Spren’s claims. Here’s what the published papers on its research page actually tested.

The image studies Spren lists

Three of the papers on Spren’s research page are peer-reviewed and indexed in PubMed Central. In each, an image-analysis program estimated body volume from a photo, and that estimate then went into a multi-compartment lab model:

• A 2021 study in Medicine and Science in Sports and Exercise tested 67 adults aged 18 to 39. Body volume from the image averaged 67.76 L against 67.72 L from underwater weighing, which was not significantly different.
• A 2022 study in the European Journal of Clinical Nutrition tested forty-eight participants averaging 22.9 years old. The authors concluded the program gave an accurate estimate of body volume, and of body fat within a 3-compartment model, “in generally healthy, young adults.”
• A 2022 study in the Journal of Clinical Densitometry tested 57 participants averaging 22.5 years old, 84.2% of them White. It compared the image-based model and DXA against a 5-compartment lab criterion, and the image-based model “performed slightly better in our sample of young adults than the DXA 3C model.”

Two details matter when you read those results as an app user. First, in the Journal of Clinical Densitometry study, the image-based model “included measures of total body water derived from bioimpedance spectroscopy,” a lab measurement taken alongside the photo. Second, the samples were young, generally healthy adults. None of these designs tells you how a selfie alone performs for an older, heavier or more diverse group.

What independent research says about photo apps in general

A 2026 review in Nutrition identified 11 apps for body composition prediction from 18 studies. The apps “demonstrated good accuracy in predicting fat mass percentage,” but most showed reduced accuracy in people with higher body fat. The review also lists “reduced accuracy at the individual-level, insufficient validation across diverse populations, and limited evidence on longitudinal tracking capabilities.”

That applies to every photo-based app, Corpus included. Treat one reading as an estimate and read the trend.

Spren and Corpus side by side

	Spren	Corpus
How you capture	A full-body selfie	A guided photo check-in, with Photo Match checking framing, pose, distance and lighting
What you get back	PDF report: body fat %, fat mass, lean mass, A/G fat ratio, resting metabolic rate	Estimated body fat, FFMI, eight muscle-group views and a score, next to your photos
Extras	Nutrition targets, 24/7 AI coaching, HRV scans	Coach and next-step guidance; optional Apple Health recovery context (sleep, HRV, resting heart rate)
Platform	iPhone, iOS 17 or later	iPhone, iOS 26 or later
Price (US)	Free download; in-app purchases listed at $10.49 to $119.99	$49.99 a year with a 14-day trial, or $7.99 a month
Evidence on accuracy	Spren says results are comparable to DEXA; its listed image studies tested young adults, inside lab models	No published validation yet
Ads and tracking	App Store privacy label: usage data may be used to track you across other companies’ apps and websites	No ads or ad tracking

Where Corpus is different

Corpus is a photo-based iPhone app, so the review’s caution about individual accuracy applies to it too. The methodology page says what its estimates can and can’t do. What it’s built around:

• Weekly check-ins, priced for them. At $49.99 a year, that’s about $0.96 per weekly check-in, with no clinic visit.
• Capture consistency. Photo Match evaluates framing, pose, distance and lighting against your earlier check-ins, because a consistent capture is what makes a photo trend readable.
• A visual record next to the numbers. Your photos sit beside the estimated body fat, FFMI and muscle-group views they produced, so you can see the change as well as read it.
• Recovery context, if you want it. Connect Apple Health and sleep, HRV and resting heart rate appear next to your composition trend. It’s optional.
• No ads. Corpus is supported by subscriptions, and check-in data isn’t used to target ads.

Which should you choose?

• You want one accurate reading or bone density: book a DEXA scan; DEXA scan alternatives explains how home methods compare.
• You want a body-fat number plus resting metabolic rate and nutrition targets: Spren covers that in one app.
• You’re on an older iPhone that can’t update to iOS 26: Spren, since it supports iOS 17 or later.
• You’re comparing more apps and methods first: see the best ways and apps to track body composition.
• You want a weekly composition trend you can see, with consistent photos, FFMI and muscle-group views, and no ads: that’s what Corpus is built for. Check in the same way every week and read the trend; how often to measure body composition explains why weekly is enough.