---
title: "Best mix"
description: "Finding the mix for a target depth from your ppO₂ limit and your own narcosis and density targets."
---

> Documentation Index
> Fetch the complete documentation index at: https://docs.divelogic.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Best mix

import { BestMixScreen } from "@/components/react/ToolScreens";

Best mix answers *what should I breathe at this depth?* Give it a depth, an
oxygen limit and two targets, and it returns the mix that sits on those limits
there. It is [Mix at depth](/tools/mix-at-depth) run backwards.

## What you enter

- **Depth** (m): the deepest point the mix has to work at.
- **Max ppO₂**: 1.2, 1.4 or 1.6 bar at that depth.
- **Max EAD** (m): the narcosis target. The tool adds helium until the EAD is
  at or below it.
- **Max density** (g/L): the density target, handled the same way.

The **Targets** group notes that 30 m EAD and 5.2 g/L are common technical
limits. Unlike the calculator in the planner's gas wizard, both targets here
are yours to change.

## Reading the result

- **Breathe**: the mix, named as divers name it: *Air*, *EAN32*,
  *Trimix 18/45*.
- **Oxygen** and **Helium** (%): the two fractions, as whole percentages.
- **EAD** (m) and **Density** (g/L): what the mix gives at the depth, with your
  target beside each.
- **The composition bar**: the O₂, He and N₂ split, with each share in figures.

The mix is decided in two moves. Oxygen comes first: the richest whole
percentage your Max ppO₂ allows at the depth, rounded down so the ppO₂ lands at
or below your limit. Helium is then the least that meets both targets, rounded
up, and whichever target needs more sets it. The verdict says which one did:
past roughly 50 to 60 m it is usually density.

## What it does not check

- **The surface.** A mix for 60 m at 1.3 bar comes to 18 % oxygen, too lean to
  breathe at the surface, and nothing says so. A hypoxic mix needs a travel gas.
- **Decompression.** The result is a bottom mix for one depth. Deco gases and
  their switch depths are separate decisions.
- **What can be filled.** The answer is what the limits ask for, not a mix
  rounded to what your blender stocks. Put the analysed mix, not this one, into
  a plan.

## Next

- [Mix at depth](/tools/mix-at-depth) checks a mix you already have.
- [Partial-pressure fill](/tools/partial-pressure-fill) turns the result into a
  fill.
- [Best mix in the planner](/gases/best-mix) covers the gas wizard's version.

Source: https://docs.divelogic.ai/tools/best-mix/index.mdx