# Illuminance Meter vs Just Calc.

The clearest difference is ads: Illuminance Meter at none against Just Calc.'s shown. Just Calc.'s advantage is update cadence (weekly vs every 3 months). On price, in-app purchases, device support and iOS requirement there is nothing between them.

Both are free to download. Illuminance Meter sells 3 in-app purchases, starting at $3.99 per 7 days and Just Calc. sells 9 one-off in-app purchases. Whichever you choose, the download price is not the number that matters.

Illuminance Meter ships an update every 3 months, Just Calc. weekly. The most recent releases landed on November 12, 2026 and November 10, 2026 respectively.

## The numbers

| Metric | Illuminance Meter | Just Calc. |
| --- | --- | --- |
| Price | Free | Free |
| Positive reviews | 0.0% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | **No** | Yes |
| Update frequency | Every 3 months | **Weekly** |
| Monetization | Free with in-app purchases | — |
| Size | 13 MB | 9 MB |
| Requires iOS | **17.0** | 18.0 |
| Devices | iPhone | **iPhone, iPad** |
| Age rating | 4+ | 4+ |
| Developer | [LEAN ASIA CO., LTD](https://appshunter.io/developer/1815050814) | [Yuqin Lin](https://appshunter.io/developer/6822245171) |

## What reviewers say

### Illuminance Meter

[App page](https://appshunter.io/ios/app/illuminance-meter-lux-ppfd/id6759972986)

Transform your iPhone into a professional light meter to measure illuminance in lux or foot-candles. Ideal for photographers, plant enthusiasts, and workplace safety, it provides instant, accurate light readings with various specialized modes and data export options.

**Highlights:** Real-time lux measurement with live gauge, Photography mode for exposure value (EV) calculation, Plant light mode with recommendations, Workplace standards verification, Measurement history with export options, Spectrum analysis for color temperature and CRI, Multiple illuminance unit switching

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium Weekly Plan | $3.99 | per 7 days |
| Premium Yearly | $19.99 | per year |
| Lifetime | $39.99 | one-time |


### Just Calc.

[App page](https://appshunter.io/ios/app/just-calc/id6822245169)

**Features:** macOS Compatibility, Family Sharing

**In-app purchases (9)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Minimalist | $0.99 | one-time |
| Color Blocks Pack | $0.99 | one-time |
| Neo Brutal Pack | $0.99 | one-time |
| Y2K Desktop Pack | $0.99 | one-time |
| Retro OS Pack | $0.99 | one-time |
| Pixel Pastel Pack | $0.99 | one-time |
| Doodle Pack | $0.99 | one-time |
| Summer Comic Pack | $0.99 | one-time |
| Unlock Premium | $7.99 | one-time |


## Frequently asked questions

### Is Illuminance Meter free?

Illuminance Meter is free to download, with in-app purchases available.

### Is Just Calc. free?

Just Calc. is free to download, with in-app purchases available.

### Do Illuminance Meter or Just Calc. have ads?

Just Calc. shows ads; Illuminance Meter does not.

### Which is updated more often, Illuminance Meter or Just Calc.?

Illuminance Meter ships an update every 3 months, and Just Calc. weekly. Most recently, Illuminance Meter was updated on November 12, 2026 and Just Calc. on November 10, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*