# Diffraction Grating Calculator vs D4H Personnel & Training

The clearest difference is price: D4H Personnel & Training at Free against Diffraction Grating Calculator's $2.99. D4H Personnel & Training also leads on update cadence (every 3 weeks vs every 29 months). Diffraction Grating Calculator's advantage is iOS requirement (13 vs 15.6). On ads, in-app purchases and device support there is nothing between them.

D4H Personnel & Training is free to download; Diffraction Grating Calculator costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Diffraction Grating Calculator ships an update every 29 months, D4H Personnel & Training every 3 weeks. The most recent releases landed on October 29, 2026 and November 2, 2026 respectively.

## The numbers

| Metric | Diffraction Grating Calculator | D4H Personnel & Training |
| --- | --- | --- |
| Price | $2.99 | **Free** |
| Rating | — | **[2.0 (19 ratings)](https://appshunter.io/ios/app/d4h-personnel-and-training/id1456365440/reviews)** |
| Number of ratings | — | **19** |
| Positive reviews | — | 10.5% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 29 months | **Every 3 weeks** |
| Monetization | — | Free |
| Size | 1 MB | 35 MB |
| Requires iOS | **13** | 15.6 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Nitrio](https://appshunter.io/developer/321121189) | [D4H Technologies](https://appshunter.io/developer/906381108) |

## What reviewers say

### Diffraction Grating Calculator

[App page](https://appshunter.io/ios/app/diffraction-grating-calculator/id1413088894)

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

**In-app purchases:** none


### D4H Personnel & Training

[App page](https://appshunter.io/ios/app/d4h-personnel-and-training/id1456365440)

Manage personnel, qualifications, training, and availability for your response team. This proactive system helps measure performance and engage staff to ensure a high standard of professionalism.

**Highlights:** Personnel management, Qualification tracking, Training administration, Attendance monitoring, Availability management, Performance measurement, Collaborative engagement

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

**In-app purchases:** none


## Frequently asked questions

### Is Diffraction Grating Calculator free?

Diffraction Grating Calculator costs $2.99, with no in-app purchases.

### Is D4H Personnel & Training free?

D4H Personnel & Training is free to download, with no in-app purchases.

### Do Diffraction Grating Calculator or D4H Personnel & Training have ads?

Neither Diffraction Grating Calculator nor D4H Personnel & Training shows ads.

### Which is updated more often, Diffraction Grating Calculator or D4H Personnel & Training?

Diffraction Grating Calculator ships an update every 29 months, and D4H Personnel & Training every 3 weeks. Most recently, Diffraction Grating Calculator was updated on October 29, 2026 and D4H Personnel & Training on November 2, 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.*