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summer worsley

Summer Worsley, Dive Instructor


The Suunto D4i

The Suunto D4i is a great all-rounder offering air, nitrox, and now an innovative ‘freediving’ (FREE) mode. Whether you’re a scuba junkie, a freediving fanatic or both, this stylish and easy-to-use dive watch will appeal to you.

The popular Suunto D-series doesn’t disappoint with the D4i. Its many features include the option of wireless tank pressure and remaining air time readouts; a great feature for those looking for that technological edge.

suunto d4i

Where to Buy:

We’ve done all the work for you and found the best prices on the Suunto D4i:

Our recommendations:

The D4i looks robust and comes with an elastomer strap, ensuring maximum comfort and fit. As its lightweight and compact design make it perfect to wear as a watch, there’s no excuse for forgetting your dive computer! Wherever your underwater adventures take you, the D4i is sure to be a reliable buddy.

If you’ve already got your heart set on the D4i, click on the link above for the latest prices and full details.

Read the complete list of the best Dive Computers here!

suunto d4i

White Suunto D4i on the go!

Photograph from

Suunto D4i Dive Computer: Key Specifications

  • Four modes including air, nitrox, freediving and off
  • Dot matrix display for great visibility
  • Apnea timer plus a timer in air and Nitrox modes
  • Optional air integration feature for current cylinder pressure and remaining air time
  • Lightweight and compact
  • Suunto RGBM decompression model
  • Audible diving alarms
  • Useful dive planner
  • User updatable firmware.
  • Detailed logbook and dive data. Downloadable to your PC or Mac using Suunto’s DM5 software.
  • ifferent data for freediving and scuba diving
  • Altitude adjustments
  • Conservatism settings
  • Daily alarm clock function to get you to the dive site on time

Which is Better, the Suunto D4i or the Suunto D4i Novo?

Suunto has recently redesigned its popular D4i, introducing the D4i Novo. It’s a stylish dive watch available in a variety of fresh colors and comes with a silicone strap. Is the D4i Novo really superior to its predecessor? Or, at 25 percent more expensive, are Suunto simply cashing in on the fashion conscious customer?

Let’s take a look at some of the differences.

Really, we can’t find much to differentiate these two models other than the mostly cosmetic changes.

  • The Novo comes with a USB cable, whereas the D4i doesn’t, this could help to explain the price difference
  • The straps are made from different materials, now silicone instead of the D4i’s elastomer strap
  • The Novo is slightly heavier, weighing around a quarter ounce (7 grams) more than the D4i.
  • The Novo’s buttons are metal as opposed to the D4i’s plastic buttons

Apart from the above, both computers share the same features and functionality. 

Black & Lime Suunto D4i on wrist

Photograph from
suunto d4i

What You Need to Know About the Suunto D4i

After test diving the D4i, these are the key features we found particularly useful:

The Suunto D4i is Compact

We love the fact that dive computer designs are now the size and style of a wristwatch. We no longer have to rely on old bulky computers which have a potential to make one feel more like an astronaut than a diver.

The D4i measures 1.91in/48.6mm in diameter is 0.63in/16mm thick and weighs a mere 3oz/85g, allowing it to sit nicely on your wrist. Modern-day divers are looking for ways to streamline their dive equipment as much as possible and now your computer can do the same. Think in terms of moving from a desktop to a laptop, could you ever go back?

It’s also nice to have a computer that you can wear day in and day out as a watch.

Clear and Easy to Navigate

The smaller design does not compromise the screen’s visibility or ease of functionality. If you’re deliberately avoiding a smaller computer for that reason, you may want to check out the D4i. The dot matrix display is bright and clear and we have no problems viewing it and operating the menu underwater.

The electroluminescent backlight feature is super useful for night dives and low visibility conditions.

‘Free’ Dive Mode

Suunto has really listened to the ever-growing freediving community and made sure its D4i has a dedicated freediving mode (marked ‘FREE’ on the computer).

As a freediver tends to move through the water a lot quicker than a scuba diver, the sample rates of three times per second mean the D4i can easily keep up with their pace. It can also register that a dive is in progress very quickly.

The D4i’s new surface alarm, along with the staple multi-depth and time settings, means that freedivers don’t have to look at their computers as much. We can imagine that’s a great bonus in terms of concentrating on mindfulness, not the technology tracking the dives.

Nitrox Compatible

The D4i is EANx compatible, allowing you to maximize your dive time by adjusting the oxygen percentage between 21% and 50% and your ppO2 limit between 1.2 and 1.6 bar. After diving on Nitrox mode and setting your oxygen content to 22% or higher, the computer will not automatically go back to 21%, so make sure you manually adjust it.

Alarms and Warnings

The Suunto D4i dive computer allows you to customize all the diving alarms such as ascent rate and maximum depth. In the FREE mode, you can set the depth notification alarm to indicate a certain depth.

For low-air-pressure warnings (when diving with a transmitter), the computer will alert the diver with a blinking pressure display and two audible double beeps when the remaining air reaches 50 bar/700 psi. It also emits two double beeps when the cylinder pressure hits the user-selected alarm pressure and when the remaining air time reaches zero.

The ascent rate is displayed in a vertical bar running up the right-hand side of the display. When the maximum allowable ascent rate is exceeded, the lower segment of the bar starts to blink and the top segment stays solid.

Optional Wireless Air Integration

The D4i features wireless air integration. The optional Suunto Transmitter is easy to install in your regulator’s first-stage HP port. The transmitter provides a remaining air time (RAT) feature that calculates tank pressure, depth, and decompression status to tell you how long you can stay underwater.

When using the transmitter, the computer displays available gas pressure from 0 to 5000 psi (0 to 350 bar).

This innovative technology means that all the information you need is on your wrist, leaving you more time to look at what you’re really down there for.

Personal and Altitude Adjustments

D4i users can easily adjust their current altitude and make personal adjustment settings. These are displayed on the startup screen when entering the DIVE mode. Use the personal adjustment factors (P1 and P2) to add an extra level of conservatism, if you prefer.

Suunto D4i simple yet elegant design

Photograph from
suunto d4i

The Suunto D4i’s Decompression Model

The Suunto D4i runs a reduced gradient bubble model (RGBM) algorithm, which was developed in conjunction with the eminent bubble specialist, Dr. Bruce R. Wienke. Suunto has been working with Dr. Wienke since the late 90s to produce this modern, pioneering algorithm which is at the heart of its recreational dive computers.

The RGBM model, which is aimed at recreational divers, uses a simple set of M-values to compute decompression profiles. This works by predicting both dissolved and free gas in a diver’s tissues and bloodstream.

Suunto’s model accounts for diving behaviors that increase health risks. It addresses factors such as continuous multi-day diving, repetitive diving, reverse profiles, and ascent-rate violations, which produce high microbubble buildup. The model is based on both laboratory experiments and diving data, including data from DAN. Its reliability is proven by millions of successful dives.

What Does This Mean for the Diver?

To break down what this means, let’s first look at what an algorithm is. You should remember learning about the Recreational Dive Planner (RDP) as a novice diver, and, hopefully, how to use it. The RDP was developed by the Navy and is inconsistent with how divers actually dive. For instance, we do not generally spend set times at certain depths.

The algorithm built into your dive computer uses a depth sensor and a timer to work out how much gas is theoretically being absorbed and expelled at any given time. This data then produces your no decompression limit (NDL).

The Suunto RGBM provides a model of what is happening in your body throughout a dive based on your actual profile. You may find Suunto’s algorithm more conservative than computer brands which use different algorithm models. For example, Oceanic’s Pelagic DSAT is less conservative with increased NDL limits.

This isn’t to suggest that other models are dangerous and Suunto’s version is safer, just that Suunto’s RGBM has taken the most extreme factors into consideration. All this means is that Suunto computers may provide shorter dive times before reaching the NDL than other brands.

Conservative doesn’t have to be a bad thing though, we believe that you should always err on the side of caution when your health is involved.

The RGBM model requires safety stops in a 3-6m/10-20ft depth zone on all dives deeper than 10m/30ft, uses ascent rates that do not exceed 10m/33ft per minute, restricts repetitive exposure, restricts reverse profiles and deep spike diving, and restricts multi-day activity.

Suunto’s After Sales and Servicing Support

Suunto has an excellent reputation for reliable after-sales and servicing support for all its products. You can find information on service and repair centers, or how to send your item to the company on their website. In the very worst case scenario, if there are no service centers in your country, your computer may have to travel to Finland. But this is unlikely.

Suunto offers a two-year international warranty (from the date of purchase) on all their products. To qualify, you first need to register your product on their website. Upon registering you will also stay up to date with any safety and system updates.

Suunto D4i – How to change Nitrox mode and set up Nitrox gas

Any Ongoing Maintenance?

The Suunto Dive computer is a sophisticated precision instrument and you should treat it with care. These computers are built to withstand the rigors of scuba diving, however, you still need to keep your computer clean by rinsing it thoroughly in fresh water after each use.

Never attempt to open the computer case yourself and take it to a Suunto service center at least every two years, or 200 dives, for regular servicing and a battery change.

For help changing the settings on your D4i computer, check out Suunto’s website for a series of how to videos including ‘how to change transmission code’, ‘how to change dive settings’ and ‘how to set alarms.’

For more information take a look at the Suunto D4i User Guide


Before we come to the end of our Suunto D4i dive computer review, let’s have a roundup of the key points including what we love and what we wished the computer had.

Manufacturer’s Specs and Features:

  • Suunto RGBM decompression algorithm
  • Four diving modes: air, nitrox, free, and off
  • Dedicated apnea timer and a timer in both air and Nitrox modes
  • User updatable firmware
  • An optional wireless air-integration feature
  • In-built dive planner
  • Logbook function for both freediving and scuba diving. Downloadable via USB to PC or Mac with the appropriate Suunto software.
  • Weight: 85g/3oz
  • Depth rating: 100m/328ft
  • Battery life (assuming 100 or so dives per year) around a year and a half
  • Time and date
  • Stopwatch
  • Backlit
  • EANx compatible

What We Like:

  • Great size, it’s an elegantly put together computer. We’re happy to wear it as a watch
  • Freediving mode offers versatility, well suited to those who scuba dive and freedive
  • Easy to read display and intuitive buttons and controls
  • Very reasonably priced for what it can do
  • An optional USB cable, if you don’t want it, don’t buy it. Save some cash for more dives!

What We Don’t Like:

  • The elastomer strap may become weak, more so than other material.
  • The tank pressure transmitter had problems linking if the tank was turned on too rapidly. But this is true for many transmitters
  • Only available in black
  • No built-in compass, however, this is a mid-range computer so we can’t complain

Buy This Computer If:

Overall we loved this computer. If you’re into both recreational scuba and freediving, then you can’t go wrong with the Suunto D4i. It does everything you need it to do and for a reasonable price.
As we said at the beginning of this review, the D4i is known as a great all rounder and we agree with that reputation. It’s also an impressive looking bit of kit which you can wear all the time. That might sound a little shallow, but let’s face it, we love to impress our non-diving buddies too!

suunto d4i
The Suunto D4i in different color, photo from

Where to Buy:

We’ve done all the work for you and found the best prices on the Suunto D4i:

Our recommendations:

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