Mix Result

What it is

The Mix Result tool answers a forward question: “I have this gas in my cylinder, I add that gas on top, what do I end up with?” You set the cylinder’s current contents and pressure, list the gases you’re adding, and the tool gives you the resulting mix and final pressure after each addition.

The in-app title is “Mix Result” (the home card calls it “Mix Result” with the hint “What mix do I get?”). It lives at the plan/mix-calculator route.

How this differs from the Gas Blender

These two tools run the same physics in opposite directions, so it’s worth being clear which you want.

• Mix Result (this tool) works forwards. You know what you’re adding; it tells you the mix you’ll get. Use it to check what a top-up does, or to figure out the leftover blend in a cylinder you didn’t fully empty.
• Gas Blender works backwards. You know the mix you want; it tells you the fill steps (how much oxygen, helium, and top-up gas to add, and to what pressure) to reach that target. Use it when you’re filling to a recipe.

Reach for Mix Result when you’re starting from what’s in the cylinder. Reach for the Gas Blender when you’re starting from the mix you need.

How to use it

1. Set the current cylinder: its O₂%, He%, and pressure. Both fields are always shown, so leave He% at 0 for air or nitrox and set it for trimix or heliox. Or tap the Quick Fill picker at the top of the Current Cylinder card to fill O₂%, He%, and pressure from a saved cylinder profile in one tap (it appears only once you have at least one saved profile).
2. Add one or more gases under Add Gas, each with its own O₂%, He%, and the pressure you’re adding. The form opens pre-filled to 100% O₂ at a 5 bar increase (shown in your pressure unit), so the common “top up with oxygen” case is just setting how much to add. Press Add Gas to stack another.
3. Optionally open the collapsible Environment section to set altitude and the fill versus ambient temperature.
4. Read the Steps and the final gas. Reset clears it back to the start.

Inputs and outputs

Input	Meaning	Notes
Current O₂% / He%	What’s already in the cylinder	Both fields always show; set to 0 for nitrox, enter a value for trimix or heliox
Current pressure	Starting cylinder pressure	Gauge pressure, in your unit (bar or psi)
Added gas O₂% / He%	Composition of each gas you add	One row per addition
Added pressure	How much pressure each addition contributes	Sequential, in order
Altitude	Sets atmospheric pressure	Optional; matters for accurate blending
Fill / ambient temperature	The temperature during filling and where the gas settles	Optional; drives the cooldown/warm-up step

Output	Meaning
Starting gas	The cylinder state you began with
Steps	Step-by-step O₂%, He%, and pressure after each addition
Cool down / warm up step	The “Cool down to X” or “Warm up to X” line that appears in Steps when fill and ambient temperatures differ
Final gas	The resulting O₂%, He%, and pressure

How the math works

Mixing uses Dalton’s Law of partial pressures on absolute pressures (gauge plus atmospheric):

FO₂_final = (P_abs_current × FO₂_current + dP × FO₂_added) / P_abs_final

Helium mixes the same way. Oxygen and helium fractions don’t change with temperature, but pressure does, so the temperature correction uses Gay-Lussac’s Law:

P_settled = P_hot × (T_ambient_K / T_fill_K)

That’s why a hot fill shows a “cool down to” step and a cold fill shows a “warm up to” step. All of this runs in Decimal.js for safety-critical precision.

Pressure reads in your chosen unit (bar or psi); the calculation is metric internally and converts at the display boundary.

Behaviour and limits

The result is a calculation, not a measurement. Always analyse the finished cylinder with an oxygen (and helium) analyser before diving, and label it.

Input ranges: pressure goes up to 330 bar (4787 psi), altitude up to 10000 m, and fill and ambient temperatures from -50 to 100 C. If an addition would push the mix over 100% O₂, the tool rejects it and the result panel simply goes blank with no number shown. That blank panel is your signal that the fill is impossible as entered, not a bug. Lower the added pressure or the added O₂% until a result appears.

Related

• Gas Blender is the reverse tool: give it the mix you want and it gives you the fill steps to get there.