531 Strength vs Rhythm LightScore
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
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.
- Calculate 5/3/1 weights
- Track 1RM for exercises
- View cycle step weights
- Round weights to available plates
- Full overview of weights, reps, sets
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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.
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.
- 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
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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
Verdict
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
Both are free to download. 531 Strength sells 4 one-off in-app purchases. Rhythm LightScore asks for nothing beyond the download.
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.
531 Strength ships an update every 2 months, Rhythm LightScore every 4 days. Both last shipped on October 24, 2026.
| Parameter | 531 Strength | Rhythm LightScore |
|---|---|---|
| Price | Free | Free |
| Rating | 4.9 (12K ratings) | 5.0 (5 ratings) — better |
| Positive reviews | 94.0% of reviews | 100.0% of reviews — better |
| Number of ratings | 12K — better | 5 |
| Update frequency | Every 2 months | Every 4 days — better |
| Ads | Yes | No — better |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | Free — better |
| Devices | iPhone, iPad | iPhone, Apple Watch |
| Requires iOS | 18.0 | 18.0 |
| Further details — not scored | ||
| Size | 26 MB | 26 MB |
| Age rating | 4+ | 4+ |
| Developer | Henrik Jachobsen | Rhythm Innovations, Inc. |
Customer experience
531 Strength
Rhythm LightScore
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
531 Strength
- Additional exercises$1.99
- Adjustable set$1.99
- Plate calculator$1.99
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- Progress log$6.99
Rhythm LightScore
No in-app purchases
Questions
Is 531 Strength free?
Is Rhythm LightScore free?
Which has better reviews, 531 Strength or Rhythm LightScore?
Do 531 Strength or Rhythm LightScore have ads?
Which is updated more often, 531 Strength or Rhythm LightScore?
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