# TDF Calc vs Spine Physics

The clearest difference is update cadence: Spine Physics at every 2 days against TDF Calc's every 67 months. TDF Calc's advantage is iOS requirement (13.2 vs 15.0). On price, rating, ratings volume and ads there is nothing between them.

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

On the App Store both sit at effectively the same score — 5.0 for TDF Calc against 5.0 for Spine Physics. Both are backed by a comparable volume of ratings — 1 and 1 respectively.

TDF Calc ships an update every 67 months, Spine Physics every 2 days. The most recent releases landed on June 5, 2026 and September 10, 2026 respectively.

## The numbers

| Metric | TDF Calc | Spine Physics |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [5.0 (1 ratings)](https://appshunter.io/ios/app/tdf-calc/id312749340/reviews) | [5.0 (1 ratings)](https://appshunter.io/ios/app/spine-physics/id1566693028/reviews) |
| Number of ratings | 1 | 1 |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 67 months | **Every 2 days** |
| Monetization | Free | Free |
| Size | 2 MB | 10 MB |
| Requires iOS | **13.2** | 15.0 |
| Devices | iPhone, iPod | iPhone, iPod |
| Age rating | 4+ | 12+ |
| Developer | [Eye Physics](https://appshunter.io/developer/312749343) | [Jonathan Nakhla](https://appshunter.io/developer/1554899575) |

## What reviewers say

### TDF Calc

[App page](https://appshunter.io/ios/app/tdf-calc/id312749340)

This app calculates the biologically effective dose (BED) for radiation therapy fractionation regimens. It allows for comparisons of different treatment schedules and helps determine dose per fraction based on desired treatment duration.

**Highlights:** Linear-quadratic (LQ) method implementation, Biologically effective dose (BED) calculation, External beam radiation therapy (EBRT) fractionation, Low dose rate (LDR) brachytherapy, Permanent implant brachytherapy, Dose per fraction calculation

**Features:** macOS Compatibility

**In-app purchases:** none


### Spine Physics

[App page](https://appshunter.io/ios/app/spine-physics/id1566693028)

This app visualizes how obesity affects the body, using a teeter-totter analogy for the spine to explain the importance of maintaining a healthy abdominal girth. It serves as an educational tool for patients, drawing on a surgeon's perspective.

**Highlights:** Obesity impact visualization, Spine teeter-totter analogy, Abdominal girth importance, Surgeon's educational tool, General health information

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is TDF Calc free?

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

### Is Spine Physics free?

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

### Which has better reviews, TDF Calc or Spine Physics?

TDF Calc and Spine Physics are both rated 5.0 out of 5 on the App Store, from 1 and 1 ratings respectively.

### Do TDF Calc or Spine Physics have ads?

Neither TDF Calc nor Spine Physics shows ads.

### Which is updated more often, TDF Calc or Spine Physics?

TDF Calc ships an update every 67 months, and Spine Physics every 2 days. Most recently, TDF Calc was updated on June 5, 2026 and Spine Physics on September 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.*