Dive Calculator Manual

Version 1.11 · 1 November 2026

What is the Dive Calculator

The Easy Diving Fun Dive Calculator works out dive gases, fills, oxygen exposure and decompression plans – in the browser, on your phone and on your PC, without installation. It is made for divers, instructors and gas blenders and is based on the “Tauchtabellen” Excel workbook by Edward Lechner.

• Address: rechner.easydiving.fun
• Access: only with an activated email address, password-free login via link or code
• Full version: all 11 calculators
• Trial: some calculators usable, the others are visible and marked 🔒

This manual describes version 1.11. In the app you can open it at any time with the “Manual” button at the top right (“?” on phones). A German version is available at handbuch.html.

Getting started

Logging in

1. Open rechner.easydiving.fun.
2. Enter your email address and tap “Send login link”.
3. Open the email and tap the link – ideally on the same device and in the same browser. No email? Check your spam folder.
4. The app opens logged in. You stay logged in on this device until you log out.

At most one link per minute can be sent per address. If the address is not activated, the app says so and points to the contact form.

Log in with code (installed app): on a phone the link in the email opens the browser, not the installed app. So in the app, after “Send login link”, type the code from the email into the “Code” field and tap “Log in with code”. If you already have the email, use “I already have a code from the email”. Link and code are valid for 60 minutes.

Requesting a trial

1. Enter your email address on the login page.
2. Tap “Try N days free” (Easy Diving Fun sets the number of days, currently 14).
3. Open the link in the email.

Each address gets the trial only once. A purple band at the top shows until when it is valid. For the full version use the “Contact Easy Diving Fun” link in the band.

Installing as an app

The app shows the exact steps under “Install as app” – at the bottom of the login page and in the app footer. Choose your device and browser there; your browser is preselected.

Then open the app and log in once with the code from the email – the link in the email only opens the browser, not the app.

Offline use: after logging in online once, the calculator works for up to 21 days without internet – e.g. on holiday or at a lake without reception. A yellow band at the top then says “Offline – last checked online on …, usable for X more days”. As soon as you are online again, the app quietly checks your access and the 21 days start again. A trial still ends on its expiry date, even offline. Sending feedback only works online.

At most 3 devices

Access applies to at most 3 devices (Easy Diving Fun can change the number). Every phone, every PC and also every other browser or a private window counts as a separate device. If you log in on a 4th device, the app shows your devices with the date of last use. With “Release” you log out an old device and log in the new one – possible once a week. Otherwise Easy Diving Fun can help via the contact form. Tip: “Log out” releases a device immediately, e.g. before selling your phone.

Own logo

If Easy Diving Fun has activated it for your account, “Own logo” appears at the bottom of the app. Choose an image (landscape works best, PNG with transparent background), optionally add a name (e.g. your dive center) and tap “Save”. Your logo then replaces the Easy Diving Fun logo at the top and appears on every printout (e.g. deco plan). It is resized automatically and stored on the device – visible offline too. “Remove logo” brings back the Easy Diving Fun logo.

Logging out

“Log out” at the top right. Always log out on other people’s devices. On phones the header shows small icons instead of text: “?” = manual, arrow out of a door = log out.

Introduction, what’s new and feedback

• Tour: at the far left of the tab bar is “▶ Tour” – a picture tour through all calculators in 6 chapters (getting started, planning gases, filling, tech & CCR, deco planner, tips) with short explanations and the key terms. Use the chapter list (on phones the selector at the top) to jump straight to a slide; move on with “Next”, the arrow keys or by swiping. “Play automatically” advances every 14 seconds like a video. The tour is also available without logging in from the login page and the info page.
• Hand signals: Right next to the tour you find “✋ Hand signals” – 116 signals with drawings in 10 chapters (basics, air and emergencies, direction and movement, communication, equipment and skills, numbers and pressure, surface and boat, light signals, lake and river life, marine life). “Practice” hides and shuffles the meanings; tap a card to reveal it. “Print / PDF” gives a handout for the dive school – with your own logo if activated. The page also works offline.
• Introduction: on first start the app shows a short introduction in 4 steps: safety notice (to confirm), overview of the calculators, colours and safety, installing as an app. From step 2 you can “Skip”. View it again any time via “Introduction” at the bottom of the app.
• What’s new: the bottom of the app shows the version number and the “What’s new” button with the list of changes. After an update a “New in version … – View” notice appears once.
• Send feedback: at the bottom of the app. Choose the type (idea, bug, question, praise), write your text, “Send”. The message goes straight to Easy Diving Fun. Online only, at most 20 per day.

General use

• Tabs: the calculators sit side by side at the top. Use the ‹ › arrows to go to the previous or next calculator; on phones you can also swipe the tab bar.
• Input fields: everything you can change has a light-blue background. Enter numbers with a point or a comma – both work.
• Sliders: in the graphical calculators (Best Mix, Gas Blending, Filling) set values with − / + or the slider, or type the number directly.
• Instant results: there is no calculate button. Every change updates the result immediately.
• Values are remembered: your input stays saved on this device and is there again next time.
• Language and units: the “EN · ft” button in the header (also “Deutsch / metric” at the bottom and on the login page) opens the choice: Deutsch / English and metric (m, bar, L, °C) or imperial (ft, psi, cu ft, °F). After “Apply” the app reloads. Calculations are always the same internally – only the display is converted, and saved values are kept. On first start the app picks the device language, imperial only for US English. Imperial in detail: cylinders US-style as rated capacity (cu ft) at rated pressure (psi), e.g. AL80 = 77.4 cu ft at 3000 psi; SAC/RMV in cu ft/min; deco stops on a 10 ft grid (last stop 10 or 20 ft); partial pressures (ppO2) and gas density (g/L) stay in bar and g/L as is common internationally.
• View and sun mode: the button in the header (circle, sun or moon icon) changes the view: automatic (like the device) → sun → dark → light. Sun mode shows black on white with thick borders and bold text – easy to read outdoors on the boat or the jetty. You can also switch it on and off with “Sun mode” at the bottom. The choice is saved on the device.

Internally the app calculates pressure in bar (sea level = 1.013 bar) and depth in metres; in imperial the display is converted. Fresh water = 0.098 bar/m (34 ft/atm), salt water = 0.1 bar/m (33 ft/atm); where it matters you can choose.

The calculators

Eleven calculators, each in its own tab. Easy Diving Fun decides which of them the trial may use (default: Best Mix, Recreational, O2 Tables).

Filling warm: the fill calculators use ambient and fill temperature: p_warm = p_cold × T_fill / T_ambient (in kelvin). Example: 230 bar cold at 20 °C ambient and 40 °C fill gas → fill to 246 bar. Below every fill sequence a yellow box shows the temperatures used; the “Change temperatures →” button jumps straight to “Filling → Temperature”. Always analyse after cooling.

Analysing: “Gas Blending” and “Filling” show in red at the top and below every sub-tab: “Always analyse after filling!”. All fill values are calculated values. After filling and cooling, measure every cylinder with a calibrated analyser – O2, for trimix also He – and mark mix, MOD, date and name on the cylinder. Never dive without analysing.

Gas density: most calculators use densities at 0 °C (like the Excel workbook), the deco planner densities at 20 °C. The values therefore differ by about 7 %.

Deco Planner

The deco planner calculates a decompression plan using Bühlmann ZHL-16 with gradient factors for open circuit (OC), semi-closed (SCR) and closed-circuit rebreathers (CCR). Defaults: ZHL-16B, GF 40/80, altitude 930 m (metric) or 0 ft (imperial).

Warning and disclaimer: the first time you open the planner on a device, a red warning appears. The planner only opens after you tick “I have read the warning, am appropriately trained and use the deco planner at my own risk” and confirm. After that the warning stays collapsed at the top of the planner and briefly below every plan. Key points: decompression diving can cause serious injury or death; no model reliably prevents decompression sickness; no guarantee and no liability; for trained divers only; cross-check every plan with a second program and your dive computer.

1. Equipment and dive

• Equipment: open circuit (OC), semi-closed (SCR) or closed circuit (CCR).
• Depth in metres or feet.
• Runtime at end of bottom time: minutes from leaving the surface to the start of the ascent, descent included. Example: 40 m / 130 ft, runtime 25 = about 2 min descent + 23 min at the bottom.
• OC and SCR: bottom gas O2 and He in %, cylinder (litres, or cu ft at rated psi in imperial) for the pressure shown in the gas requirement.

2. Deco or bailout gases

Up to four gases with O2, He, “switch at” and cylinder size. Leave O2 empty = gas is not used.

• Empty “switch at” = automatic: ppO2 1.6 from 45 % O2, 1.5 at 28–44 %, otherwise 1.4, rounded down to the stop grid (3 m or 10 ft); pure oxygen from 6 m / 20 ft. Examples: EAN50 from 21 m / 70 ft, O2 from 6 m / 20 ft.
• Priority: a gas from the list is used as soon as it is breathable – even if it has less O2 than the bottom gas. If several are breathable, the one with more O2.
• A gas switch at a stop extends that stop by 2 min (only for switch depths from 7 m, i.e. not for O2 at 6 m / 20 ft).

3. CCR

• Diluent O2/He.
• Setpoint descent (low), e.g. 0.7 bar, used during the descent.
• Setpoint bottom and deco (high), e.g. 1.2 bar, used at the bottom and on the loop ascent.
• Deco setpoint (optional) with “from depth”, e.g. 1.4 from 6 m / 20 ft. Empty = as high.
• O2 consumption (metabolic, default 1 L/min) and O2 cylinder for the oxygen requirement.
• In CCR mode the gas list is called bailout gases.

The planner shows two plans: “CCR plan – deco on the loop” and “Bailout plan – failure at end of bottom time”. In the bailout plan you ascend on open circuit on the bailout gases from the end of the bottom time. If no bailout gas is breathable at the bottom depth, the plan stays on the loop to the first switch depth and shows a red warning.

4. SCR

The bottom gas is the supply gas. The loop contains less O2 than the supply gas; set this as FiO2 adjustment:

• as value: FiO2 = FsO2 − x % (default x = 2: 16/45 becomes 14/46.1)
• as factor: FiO2 = FsO2 − FsO2 · x %
• shallow and deep value with depths; linear in between.
• per phase on/off: descent, bottom, ascent (default: bottom only).

The ascent is on open circuit on the deco gases. The planner does not calculate the supply gas consumption – it depends on the unit.

5. Settings

Open “Settings for all dives (GF, altitude, speeds, SAC/RMV)”.

6. Repetitive dives (dive 2 and 3)

You can plan up to three dives in one day. At the top of the planner choose with the tabs Dive 1 / 2 / 3 which dive you are editing.

1. Choose the Dive 2 tab.
2. Set “Plan dive 2” to yes.
3. Enter the surface interval before in minutes (180 = 3 h, 1440 = 24 h).
4. Use “Copy values from dive 1” to copy all input and then change what is different – or enter everything anew. Each dive has its own equipment (OC, SCR, CCR), depth, runtime and gases.
5. For a third dive do the same in the Dive 3 tab (only when dive 2 is switched on).

The planner carries over the residual tissue loading and the remaining CNS (90 min half-time). Below the plans there is a day overview with equipment, interval, runtime, CNS and OTU per dive and the OTU for the whole day (NOAA guideline: at most 850 per day). For CCR the plan with deco on the loop is used for the history; the bailout plan shows the failure on the respective dive.

The settings (GF, altitude, speeds, SAC/RMV) apply to all dives together.

7. Reading the result

• Tiles: total runtime, deco time, first stop, CNS, OTU, gas density at the bottom.
• Profile graphic: depth over runtime, each gas in its own colour.
• Plan table: phase (desc., bottom, asc., stop, surf.), depth, time, RT (runtime), gas, ppO2, EAD/END. For stops “time” includes travel from the previous stop. Light-blue rows with ⇄ = gas switch. On the loop the ppO2 column shows the setpoint in bar. EAD/END is hidden on phones.
• Gas requirement: litres or cu ft per gas and pressure in bar or psi for the entered cylinder, without reserve. CCR: oxygen by metabolic rate; diluent is not calculated.
• Warnings appear in yellow or red above the tiles, e.g. ppO2 at the bottom, diluent above setpoint, no deep bailout gas, gas density of a gas en route, CNS above 80 %.
• Print / save as PDF: above the plan is the “Print plan / save as PDF” button. Only the plans are printed (repetitive dives each on its own page, plus the day overview) with header, date and warning – always light, on A4. To save as PDF choose “Save as PDF” as printer in the print dialog (on iPhone: Share → Print, then spread the preview with two fingers → Share/Save).

Example (metric): 40 m, runtime 25, air, deco gas EAN50 → stops 18 m to 3 m, stop ends at 28, 29, 30, 33, 37 and 50 min, OTU 40, CNS 14 %.

8. How accurate is the planner

Checked against 10 plans from established planning software (40–100 m, air, nitrox, trimix, SCR, CCR with bailout, repetitive dives after 3 h, 4 h and 24 h; metric): 8 plans agree to the minute, in two plans one stop differs by 1 minute each, the total runtime agrees. Gas requirement ±0.5 %, OTU ±2. CNS is 1–4 points above the reference, i.e. on the conservative side. In feet the same calculation is used with a 10 ft stop grid.

Limits: no travel gas, only one depth level, no VPM-B, bailout only at the end of the bottom time. The CCR plan with deco on the loop has not been cross-checked yet. The planner is no substitute for training or a dive computer.

Frequently asked questions

Liability and contact

All calculators have been checked carefully, but no liability is accepted for correctness. The results are an aid for planning and comparison. They are no substitute for training, a dive computer or a verified dive plan. Mixed-gas, decompression and rebreather diving only with appropriate training. Always analyse gases before the dive.

The Dive Calculator was programmed with the support of artificial intelligence (Claude by Anthropic); technical specifications, calculations and checking are by Edward Lechner. Legal notice and privacy: datenschutz-en.html.

Contact, full version, report a bug: Easy Diving Fun – contact

© Edward Lechner · Easy Diving Fun, Weer, Austria