# 555 Calc vs NSYS Diagnostics

The clearest difference is ads: NSYS Diagnostics at none against 555 Calc's shown. NSYS Diagnostics also leads on update cadence (monthly vs every 20 months). On price, in-app purchases, device support and iOS requirement 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, NSYS Diagnostics monthly. The most recent releases landed on June 1, 2026 and September 22, 2026 respectively.

## The numbers

| Metric | 555 Calc | NSYS Diagnostics |
| --- | --- | --- |
| 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 | **Monthly** |
| Monetization | Ad-supported | — |
| Size | 18 MB | 24 MB |
| Requires iOS | **11.0** | 12 |
| Devices | iPhone, iPad, iPod | **iPhone, iPad, iPod, Apple Watch** |
| Age rating | 4+ | 4+ |
| Developer | [Jibiki Works](https://appshunter.io/developer/556845808) | [Grigoriy Glazman](https://appshunter.io/developer/1448501053) |

## 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


### NSYS Diagnostics

[App page](https://appshunter.io/ios/app/nsys-diagnostics/id6764545220)

**Features:** Apple Watch app

**In-app purchases:** none


## Frequently asked questions

### Is 555 Calc free?

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

### Is NSYS Diagnostics free?

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

### Do 555 Calc or NSYS Diagnostics have ads?

555 Calc shows ads; NSYS Diagnostics does not.

### Which is updated more often, 555 Calc or NSYS Diagnostics?

555 Calc ships an update every 20 months, and NSYS Diagnostics monthly. Most recently, 555 Calc was updated on June 1, 2026 and NSYS Diagnostics on September 22, 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.*