---
title: "RMV from a dive"
description: "Working out your real breathing rate from one measured stretch of a logged dive, and sending it to the other consumption tools."
---

> 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.

# RMV from a dive

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

RMV from a dive answers *how much gas do I really breathe?* Give it the gauge
readings, time and average depth of one stretch of a real dive and it returns
your respiratory minute volume (RMV): the gas you breathe per minute, brought
back to surface pressure so it holds at any depth.

## What you enter

- **Size, each** (L): the water capacity of one cylinder.
- **Cylinders**: **Single**, or **Twin** for doubles or sidemount. Twin counts
  both at the same pressure.
- **Start** and **End** (bar): the gauge at the beginning and end of the
  stretch. End must be lower than Start.
- **Time** (min): how long the stretch lasted.
- **Average depth** (m): the average over the same stretch, from your dive
  computer's log.
- **Water**: **Salt** or **Fresh**.

This tool keeps its own cylinder, so you can measure on a different set from
the one the other tools use. **Water** is shared with them.

## Reading the result

- **RMV** (L/min): the main figure, surface-equivalent.
- **SAC** (bar/min): the same rate as gauge pressure, true only for this
  cylinder.
- **Gas breathed** (L): the free gas the pressure drop represents.
- **Ambient** (bar): the pressure at the average depth.

The verdict states what you breathed, for example *You breathed 1200 L of gas
in 30 minutes at 15 m.* The RMV is worked out so that it does not
under-predict that gas use, whether you use it in these tools or in the
planner.

Under the figures, a button labelled with the figure, such as **Use 16
L/min**, sends the RMV, to the nearest half litre, to
[Gas needed](/tools/gas-needed), [Turn pressure](/tools/turn-pressure) and
[Minimum gas](/tools/minimum-gas). The button then reads **In use**, and their
**Breathing** group notes that the figure was measured. Typing a new RMV in any
of them replaces it.

## Measuring a figure you can plan with

- **Choose a steady stretch.** Leave out the descent and a busy ascent; they
  are not the rate you hold at depth.
- **This is a relaxed rate.** A problem at depth raises it sharply, which is why
  Minimum gas multiplies it by a stress factor.

## Next

- [Gas needed](/tools/gas-needed) uses the figure for a dive.
- [Breathing rates](/planning/breathing-rates) is where a plan takes its RMV.

Source: https://docs.divelogic.ai/tools/rmv-from-a-dive/index.mdx