CCR MOD

CCR MOD is a dive planning tool for closed-circuit rebreather divers using trimix or nitrox fills. It runs entirely on your device — no internet connection required.

MOD Calculator
Enter your oxygen and helium percentages and your target PPO₂ to instantly see the maximum operating depth for your gas mix. The calculator evaluates all three limiting factors simultaneously — PPO₂, gas density, and equivalent narcotic depth (END) — and tells you which one is constraining your dive. Gas density at depth is shown alongside the result so you can assess work-of-breathing risk.

Trimix Blending Calculator
Calculate the exact steps needed to blend a trimix fill from your current tank contents. Enter the current mix and pressure, enter your target mix and pressure, and receive a step-by-step blending sequence: bleed, add helium, add oxygen, top with air. Pressures are calculated for each intermediate step.

Pre-dive Checklist
A CCR pre-dive checklist covering cell dates, scrubber time, cylinder pressures, O-rings, loop integrity, negative and positive pressure tests, MAVs, ADV, and more. Checklist state is saved between sessions so a partial check survives an accidental close. A warning banner is shown at the top of the checklist if any items remain unchecked.

Settings
Switch between metric and imperial display units. Configure the maximum gas density limit, maximum END, and gas component densities if your rebreather manufacturer specifies different values.

Works offline
CCR MOD is a Progressive Web App installed from the Play Store. All calculations and the checklist run locally — no data is sent anywhere, no account required, no ads.

⚠️ Safety notice: While reasonable care has been taken to ensure accuracy, independent verification of all results is strongly recommended. Dive planning tools can contain bugs. Using this application without appropriate CCR training and without verifying results may result in serious injury or death.