As of February 2015, HKL has up to 124 tram units that can be used in scheduled passenger service.
 HKL reported that it used 97 trams to operate peak-time scheduled traffic in the spring of 2013.
Additionally, there are six trams in reserve and eight in charter use.
The MLNRV I and II series (rebuilt Valmet Nr I and Valmet Nr II units), MLRV Variotram, and Valmet NrI series comprise the current backbone of the fleet, but HKL is in the process of receiving 40 new Transtech Artic units.

In 2006–12, all Valmet Nr II+ vehicles underwent a major modification process in which a 6.5 m (21 ft 4 in) low-floor midsection was added to the tram.
The type designation was changed from Nr II+ to MLNRV to reflect the modifications made, and the longer trams were re-introduced in traffic gradually as the modification works were completed.
During the process, HKL decided to also rebuild ten of the older Nr I trams in the same way, which brought the total number of MLNRV trams to 52 upon completion in mid-2014.

The fully low-floor Variotram units, acquired in 1998–2003 from Adtranz (later Bombardier) and built by Transtech Oy in Otanmäki, proved to be unreliable, causing a shortage of operable trams.
Starting in 2004, HKL purchased ten DUEWAG series second-hand trams from Mannheim in Germany to cover for the shortage.
Eventually arrangements were made with Bombardier to keep a sufficient number of the units in operation.
All of the DUEWAG units were either withdrawn or relegated to charter service by the end of 2014.
Variotrams were disabled in 2018 because they had problems in Helsinki tram network.

HKL is now in the process of acquiring 40 new low-floor Artic trams from Transtech.
They have a double-articulated, eight-axle design, are 27.3 m (89 ft 7 in) long and have 74 fixed seats, 14 foldable seats and space for 75 standing passengers.
The design has a 100% low floor and conventional, turning bogies designed to run without problems on Helsinki's challenging old-fashioned track network.
Two prototype units were delivered in 2013, and each entered passenger service approximately two months after delivery.
The first unit of the production series, no.
403, arrived in Helsinki in January 2016 and 18 units in total were delivered in 2016.
The order is worth €113 million and it includes an option for a further 90 trams.

To ease the construction of new tram tracks into Jätkäsaari beginning in 2009, HKL considered using bi-directional trams on the new line.
However, HKL decided to build the Jätkäsaari extensions with conventional return loops and to use the existing uni-directional rolling stock.
Bi-directional rolling stock will be used on the conversion of the orbital trunk bus line 550 into light rail (Raide-Jokeri) and the Crown Bridges bridge connection to Laajasalo.

The following table lists the current rolling stock.
Corresponding articles have further details about the cars in use.

Car length in meters
Car width in meters
Car height in meters with pantograph
Scheduled service
Charter service
Reserve units
Number 339 is owned by Oy Stadin Ratikat Ab.

Number 175 is a restaurant tram and is counted as charter.

A replica of Brändö Spårvägs Ab tram number 1 from 1917.

6,346 seats in scheduled service; 245 seats in charter service; 186 seats in reserve.

13,552 standees in scheduled service; 405 standees in charter service; 342 standees in reserve.

Reference for the tabular data: Finnish Tramway Society
As of February 2015, HKL has up to 124 tram units that can be used in scheduled passenger service.  HKL reported that it used 97 trams to operate peak-time scheduled traffic in the spring of 2013. Additionally, there are six trams in reserve and eight in charter use. The MLNRV I and II series (rebuilt Valmet Nr I and Valmet Nr II units), MLRV Variotram, and Valmet NrI series comprise the current backbone of the fleet, but HKL is in the process of receiving 40 new Transtech Artic units.
In 2006–12, all Valmet Nr II+ vehicles underwent a major modification process in which a 6.5 m (21 ft 4 in) low-floor midsection was added to the tram. The type designation was changed from Nr II+ to MLNRV to reflect the modifications made, and the longer trams were re-introduced in traffic gradually as the modification works were completed. During the process, HKL decided to also rebuild ten of the older Nr I trams in the same way, which brought the total number of MLNRV trams to 52 upon completion in mid-2014.
The fully low-floor Variotram units, acquired in 1998–2003 from Adtranz (later Bombardier) and built by Transtech Oy in Otanmäki, proved to be unreliable, causing a shortage of operable trams. Starting in 2004, HKL purchased ten DUEWAG series second-hand trams from Mannheim in Germany to cover for the shortage. Eventually arrangements were made with Bombardier to keep a sufficient number of the units in operation. All of the DUEWAG units were either withdrawn or relegated to charter service by the end of 2014. Variotrams were disabled in 2018 because they had problems in Helsinki tram network. 
HKL is now in the process of acquiring 40 new low-floor Artic trams from Transtech. They have a double-articulated, eight-axle design, are 27.3 m (89 ft 7 in) long and have 74 fixed seats, 14 foldable seats and space for 75 standing passengers. The design has a 100% low floor and conventional, turning bogies designed to run without problems on Helsinki's challenging old-fashioned track network. Two prototype units were delivered in 2013, and each entered passenger service approximately two months after delivery. The first unit of the production series, no. 403, arrived in Helsinki in January 2016 and 18 units in total were delivered in 2016. The order is worth €113 million and it includes an option for a further 90 trams.
To ease the construction of new tram tracks into Jätkäsaari beginning in 2009, HKL considered using bi-directional trams on the new line. However, HKL decided to build the Jätkäsaari extensions with conventional return loops and to use the existing uni-directional rolling stock. Bi-directional rolling stock will be used on the conversion of the orbital trunk bus line 550 into light rail (Raide-Jokeri) and the Crown Bridges bridge connection to Laajasalo.
The following table lists the current rolling stock. Corresponding articles have further details about the cars in use.
Car length in meters
Car width in meters
Car height in meters with pantograph
Scheduled service
Charter service
Reserve units
Number 339 is owned by Oy Stadin Ratikat Ab.
Number 175 is a restaurant tram and is counted as charter.
A replica of Brändö Spårvägs Ab tram number 1 from 1917.
6,346 seats in scheduled service; 245 seats in charter service; 186 seats in reserve.
13,552 standees in scheduled service; 405 standees in charter service; 342 standees in reserve.
Reference for the tabular data: Finnish Tramway Society
Helsinki tram network