Trimix Tools vs Sym Junk
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Trimix Tools
This app provides essential tools for divers to plan and blend Trimix gases. It calculates optimal mixes based on depth, oxygen partial pressure, and equivalent narcotic depth, and supports various cylinder filling scenarios. Calculations are available offline and can be customized with saved settings.
- Trimix blending and planning
- Depth and partial pressure calculations
- Equivalent Narcotic Depth (END) calculation
- Saltwater and freshwater support
- Cylinder filling and bleed down calculations
- Metric and Imperial system support
- Offline functionality
- Saved settings and custom mixes
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Trimix blending and planning tools that can be used where you are and when you need them. You can use these tools to plan your mixes prior to arriving at the dive shop or to fill your cylinder at the air station or on the boat. Calculations are provided for the best Trimix given a planned depth and a desired maximum partial pressure of oxygen and equivalent narcotic depth (END). You can also calculate the ceiling and maximum depths along with your END based on your planned mix. The dive planning tools support both salt water and fresh water calculations. The blending tools provide for filling a cylinder with a remaining mix (or empty) to a specified target mix using oxygen, helium and a topping mix (air or another available mix). You can also calculate the result of topping an existing partially filled cylinder with a specific topping mix (air or another available mix). There is also a Bleed Down calculator that allows you adjust an existing full or partially full cylinder to a new mix with minimal wasted gas. Trimix Tools supports calculations in both metric and Imperial/US systems of measure. Traveling on a boat or working out of network range? These tools are at hand any time you have your iPhone, iPad or iPod touch. You could, for example, easily calculate the result of topping your cylinder from your first dive with air from the boat's compressor to take advantage of any remaining mix. You also have the convenience of saved settings that you can recall at a touch and adjust to a new situation as needed. Chances are you regularly work with a specific set of mixes and common dive situations. Trimix Tools includes the convenience of saved settings that you can recall and adjust to a new situation as needed. You can also select mix values using pre-installed default mixes or your own saved custom mixes. When updating one of the mixes for a tool you are offered a list of saved mixes that you can use directly or adjust as needed. You can save the currently displayed mix by tapping on the "+" button. Just like with the saved calculations, you can re-arrange or delete any mixes in your saved list. Do you need to share your planning or blending calculations with other divers? All the tools have the ability to share the results of the calculations from within the application. You can set default email addresses and a subject Trimix Tool's settings that will be automatically added when you share a result. All END calculations (Dive Planning and Best Trimix tabs) in Trimix Tools treat oxygen as a narcotic gas by default. There is an option available under the Settings tab to change the default so that oxygen is not treated as narcotic if that is your preference. Remember you must always personally analyze your mix before diving it. This application is not a substitute for proper training and should not be used as a substitute for proper dive planning or the primary Trimix blending and planning methods taught during training. Please do not attempt to handle high pressure oxygen or fill SCUBA cylinders without proper training.
Sym Junk
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SymJunk is a fast, offline-first companion for configuring your CCR dive computer and rebreather head over Bluetooth — so you set everything up calmly on the surface instead of squinting at tiny buttons on the unit. CONFIGURE EVERYTHING, OFFLINE • Edit screens, gases, gradient factors, setpoints, deco and more — all on your phone, no connection needed. • Save presets per category and pick them with one tap. • Three colour themes; metric or imperial. ONE-TAP FLEET SYNC • Mark your handset, HUD and CCR head, then push your settings to all of them in a single sync — with a clear before/after overview of exactly what changed. • The clock and time zone are set correctly on every device. DIVE LOGS & MAP • Download your dives and view depth, temperature, pO₂ and tank-pressure profiles. • See your dives on a map. Add your own dive-site name and location to any dive — with type-ahead so your favourite sites autofill. • Dive-site totals, ranked by number of dives. OFFLINE MAPS • Download a dive area for offline use, so the map works with no signal. REBREATHER TOOLS • Live CCR-head monitor: cells, setpoint, tank pressures, battery health and more. • Vacuum/positive test with an adjustable timer and live loop Δp. • Calibration guide that follows the head live. • Step-by-step assembly and calibration checklists. WAYPOINT PLANNING • Plan waypoints on a map and upload them to your computer. PRIVACY BY DESIGN • No account, no ads, no tracking. Your data stays on your phone. The only internet use is map tiles and place-name search. SymJunk is an independent hobby app and is NOT affiliated with, or endorsed by, Halcyon or Oxygen Scientific. All brand and product names belong to their respective owners. This is experimental software and not a dive-safety device — always verify every setting on the dive computer itself and rely on your training and certified equipment. Free to use, with an optional one-time Pro upgrade for fleet sync, waypoint upload and the live head monitor.
Screenshots
Verdict
The clearest difference is price: Sym Junk at Free against Trimix Tools's $6.99. Sym Junk also leads on update cadence (every 3 days vs every 5 months). Trimix Tools's advantage is in-app purchases (none vs 1) and chart position (#117 vs unranked). On ads, device support and iOS requirement there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Sym Junk is free to download; Trimix Tools costs $6.99 up front. Sym Junk sells 1 one-off in-app purchase. Trimix Tools asks for nothing beyond the download.
Trimix Tools ships an update every 5 months, Sym Junk every 3 days. Both last shipped on September 29, 2026.
| Parameter | Trimix Tools | Sym Junk |
|---|---|---|
| Price | $6.99 | Free — better |
| Rating | 5.0 (5 ratings) — better | — |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 5 — better | — |
| Update frequency | Every 5 months | Every 3 days — better |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Paid | — |
| Best chart rank | #117 — better | — |
| Devices | iPhone, iPad, iPod, Mac — better | iPhone, iPad, iPod |
| Requires iOS | 15.6 | 15.0 — better |
| Further details — not scored | ||
| Size | 6 MB | 59 MB |
| Age rating | 4+ | 4+ |
| Developer | Greg Mclaughlin | Rogier Visser |
In-app purchases
Trimix Tools
No in-app purchases
Sym Junk
- Divejunk$6.99
Questions
Is Trimix Tools free?
Is Sym Junk free?
Do Trimix Tools or Sym Junk have ads?
Which is updated more often, Trimix Tools or Sym Junk?
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