# 555 Calc vs PLC

The clearest difference is ads: PLC at none against 555 Calc's shown. PLC also leads on update cadence (every 2 weeks vs every 20 months). 555 Calc's advantage is iOS requirement (11.0 vs 17.0). On price, in-app purchases and device support there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

555 Calc ships an update every 20 months, PLC every 2 weeks. The most recent releases landed on September 27, 2026 and October 6, 2026 respectively.

## The numbers

| Metric | 555 Calc | PLC |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.0 (3 ratings)](https://appshunter.io/ios/app/555-calc/id868058244/reviews)** | — |
| Number of ratings | **3** | — |
| Positive reviews | 50.0% of reviews | — |
| In-app purchases | No | No |
| Ads | Yes | **No** |
| Update frequency | Every 20 months | **Every 2 weeks** |
| Monetization | Ad-supported | — |
| Size | 18 MB | 4 MB |
| Requires iOS | **11.0** | 17.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, Mac |
| Age rating | 4+ | 4+ |
| Developer | [Jibiki Works](https://appshunter.io/developer/556845808) | [spiritdev Softwareentwicklung GmbH](https://appshunter.io/developer/1530950669) |

## What reviewers say

### 555 Calc

[App page](https://appshunter.io/ios/app/555-calc/id868058244)

This utility app helps engineers and hobbyists calculate resistor values for circuits using the Timer IC 555. Simply input frequency, duty ratio, and capacitor values to get the required resistor outputs.

**Highlights:** Calculate resistor values, Input frequency, Input duty ratio, Input capacitor value, Timer IC 555 circuit design

**Features:** macOS Compatibility

**In-app purchases:** none


### PLC

[App page](https://appshunter.io/ios/app/plc-inspector/id6756433005)

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is 555 Calc free?

555 Calc is free to download, with no in-app purchases.

### Is PLC free?

PLC is free to download, with no in-app purchases.

### Do 555 Calc or PLC have ads?

555 Calc shows ads; PLC does not.

### Which is updated more often, 555 Calc or PLC?

555 Calc ships an update every 20 months, and PLC every 2 weeks. Most recently, 555 Calc was updated on September 27, 2026 and PLC on October 6, 2026.

---

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