# 555 Calc vs HE.FMX

The clearest difference is ads: HE.FMX at none against 555 Calc's shown. 555 Calc's advantage is update cadence (every 20 months vs every 42 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, HE.FMX every 42 months. The most recent releases landed on October 28, 2026 and October 26, 2026 respectively.

## The numbers

| Metric | 555 Calc | HE.FMX |
| --- | --- | --- |
| 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 42 months |
| Monetization | Ad-supported | — |
| Size | 18 MB | 37 MB |
| Requires iOS | 11.0 | 11.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Jibiki Works](https://appshunter.io/developer/556845808) | [Guido brancalion](https://appshunter.io/developer/1437358019) |

## 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, Vision Pro support

**In-app purchases:** none


### HE.FMX

[App page](https://appshunter.io/ios/app/hefmx/id1437358020)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is 555 Calc free?

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

### Is HE.FMX free?

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

### Do 555 Calc or HE.FMX have ads?

555 Calc shows ads; HE.FMX does not.

### Which is updated more often, 555 Calc or HE.FMX?

555 Calc ships an update every 20 months, and HE.FMX every 42 months. Most recently, 555 Calc was updated on October 28, 2026 and HE.FMX on October 26, 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.*