Comparison

531 Strength vs Rhythm LightScore

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

531 Strength

This app simplifies tracking your progress on the 5/3/1 strength training program. It calculates and displays weights, reps, and sets based on your one-rep max, allowing you to easily plan and execute your workouts. Rounding options help match available gym plates.

Highlights
  • Calculate 5/3/1 weights
  • Track 1RM for exercises
  • View cycle step weights
  • Round weights to available plates
  • Full overview of weights, reps, sets
Features
Read full description

Makes it quick and easy to get a full overview of all weights, reps and sets based off your 1RM when you’re following the 5/3/1 program. - Save your current 1 RM for each of the four exercises - View calculated weights for each step in the cycle - Round the weight to match the plates you have available This app is made for people who are familiar with the structure of the 5/3/1 program and who needs simple access to the calculated weights for each exercise.

About

Rhythm LightScore

This app provides a daily "LightScore" based on your exposure to daylight, its consistency, and your pre-bedtime phone use. It offers insights into your light habits and suggests improvements for better well-being.

Highlights
  • Daily LightScore out of 100
  • Measures Light Time, Consistency, and Dark Time
  • Integrates with Apple Watch Health data
  • Uses phone camera as a light meter
  • Visualizes daily progress with Sol character
  • Sunset photo capture and sharing
Features
Read full description

Your LightScore is one number for the light you actually got today: how much daylight, how early it reached you, and how steady your days are. Rhythm measures it for you, scores the day against the sun rather than the clock, and names the one thing worth doing about it. YOUR LIGHTSCORE Each day gets a LightScore out of 100, built from three parts. Light Time is how much daylight you get, and when. Consistency is how steady your daylight is day to day. Dark Time, if you connect Screen Time, is based on phone use in the hour before bed. Tap any part of the ring to see its history by week, month, six months or year. MEASURED, NOT LOGGED If you wear an Apple Watch, Rhythm reads its Time in Daylight from the Health app. Nothing to remember, nothing to tap. If you don't, your phone's front camera becomes a light meter: hold it facing you, and the minutes you measure count toward your LightScore. MEET SOL Sol, a hand-drawn sunflower, lives in your daylight ring and keeps pace with your day: stretching at sunrise, standing tall when you reach your goal, asking for light when you fall behind. Tap Sol and see what happens. THE LIGHT METER A live lux readout that tells you what a room is actually worth. An overcast window is a hundred times brighter than a well-lit office, and it takes a meter to believe it. The app itself is painted by the light you're in, so the screen changes as you walk to the window. SUNSET LOG Catch the sunset and keep the sky. Rhythm suggests the photos you took around sunset, and turns your week of skies into one image to share. PHONE USE BEFORE BED Connect Screen Time to see your phone use in the hour before bed, and how it shapes your Dark Time. The report stays on your phone. FOR THE RHYTHM LIGHT Rhythm makes a 100,000-lux sunlight generator for indoor days. With one at home, the app turns it on and off, sets its brightness, runs routines that follow sunrise and sunset on the days you choose, and can ring a wake alarm after your light comes on. Everything else works without it. ON APPLE WATCH Today's daylight and Sol on your wrist, read straight from Health. HONEST ABOUT WHAT IT KNOWS Coverage sits next to every finding ("15m in the light today, measured across 3 check-ins"), so a sampled day never passes as a watched one. The camera reading is an estimate, good to a band rather than to the lux, and the app says so plainly. PRIVACY As a light meter, the camera reads exposure settings, not pixels: no photo or video is captured, and it runs only while the app is open. Sunset photos stay on your phone unless you share them. Rhythm never writes to Health; it reads Time in Daylight and your sleep schedule, nothing else. Your readings are stored with your account so your history survives a new phone, and Delete Account removes all of it, from inside the app. Rhythm is a wellness app. It does not diagnose, treat, cure or prevent any condition, and it is not a substitute for medical advice.

Screenshots

531 Strength4 screens
Rhythm LightScore4 screens

Verdict

The call

The clearest difference is in-app purchases: Rhythm LightScore at none against 531 Strength's 4. Rhythm LightScore also leads on ads (none vs shown) and update cadence (every 4 days vs every 2 months). 531 Strength's advantage is ratings volume (12K vs 5). On price, rating, review sentiment and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. 531 Strength sells 4 one-off in-app purchases. Rhythm LightScore asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

On the App Store both sit at effectively the same score — 4.9 for 531 Strength against 5.0 for Rhythm LightScore. That said, the two scores are not equally well evidenced: 531 Strength has 12K ratings behind it against 5, so its average is the more settled of the two. Written reviews are what separate them: 94% of 531 Strength's written reviews are positive against 100% of Rhythm LightScore's.

UpkeepUpdate frequency

531 Strength ships an update every 2 months, Rhythm LightScore every 4 days. Both last shipped on October 24, 2026.

Scorecard5 real differences · 5 level
531 Strength versus Rhythm LightScore: the parameters behind the verdict, then further details
Parameter531 StrengthRhythm LightScore
PriceFreeFree
Rating4.9 (12K ratings)5.0 (5 ratings) — better
Positive reviews94.0% of reviews100.0% of reviews — better
Number of ratings12K — better5
Update frequencyEvery 2 monthsEvery 4 days — better
AdsYesNo — better
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree — better
DevicesiPhone, iPadiPhone, Apple Watch
Requires iOS18.018.0
Further details — not scored
Size26 MB26 MB
Age rating4+4+
DeveloperHenrik JachobsenRhythm Innovations, Inc.

Customer experience

531 Strength

All ratings11,645 ratings
Positive98.0%
Neutral1.2%
Negative0.8%
Written reviews282 reviews
Positive94.0%
Neutral2.8%
Negative3.2%

Rhythm LightScore

All ratings5 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews2 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

Bugs and requests

531 Strength

Reported bugs

2 issues
  • Rest timer stops when app is backgrounded
  • Plate calculator not flexible enough

Requested features

4 requests
  • Ability to adjust training max separately from 1RM
  • Option to track rep PRs and estimated 1RM
  • Accessory exercise tracking and planning
  • Sync progress across devices

Rhythm LightScore

Not enough reviews yet to summarise bugs or requests.

In-app purchases

4 purchases

531 Strength

One-time4
  • Additional exercises$1.99
  • Adjustable set$1.99
  • Plate calculator$1.99
Show 1 more
  • Progress log$6.99
None

Rhythm LightScore

No in-app purchases

Questions

Is 531 Strength free?
531 Strength is free to download, with in-app purchases available.
Is Rhythm LightScore free?
Rhythm LightScore is free to download, with no in-app purchases.
Which has better reviews, 531 Strength or Rhythm LightScore?
Rhythm LightScore is rated higher. 531 Strength averages 4.9 out of 5 from 12K ratings, while Rhythm LightScore averages 5.0 from 5 ratings.
Do 531 Strength or Rhythm LightScore have ads?
531 Strength shows ads; Rhythm LightScore does not.
Which is updated more often, 531 Strength or Rhythm LightScore?
531 Strength ships an update every 2 months, and Rhythm LightScore every 4 days. Most recently, 531 Strength was updated on October 24, 2026 and Rhythm LightScore on October 24, 2026.

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