What Type of RAM (Memory) to Use for Your iMac

To determine what kind of RAM (memory) is needed for your iMac select the model you have from the list below.

iMac G3 (233, 266, 333 MHz)
iMac G3 (350, 400, 500, 600 MHz)
iMac G4 (700, 800 MHz)
iMac G4 (1.00, 1.25 GHz)
iMac G5 (1.60, 1.80 GHz)
iMac G5 (1.9, 2.1 GHz)
iMac Intel Core Duo
iMac Intel Core 2 Duo (1.83 GHz)
iMac Intel Core 2 Duo (Late 2006)
iMac Intel Core 2 Duo (Mid 2007)
iMac Intel Core 2 Duo (Early 2008)
iMac Intel Core 2 Duo (Early 2009)
iMac (21.5-inch and 27-inch, Late 2009)
iMac (21.5-inch and 27-inch, Mid 2010 and Mid 2011)
iMac (27-inch, Late 2012 to Mid 2015)
iMac (Retina 5K, 27-inch, Late 2015)
iMac (Retina 5K, 27-inch, 2017)
iMac (Retina 5K, 27-inch, 2019)
iMac (Retina 5K, 27-inch, 2020)



iMac G3 (233, 266, 333 MHz)
Maximum Memory: 512 MB
Memory Type: 144-pin SODIMM SDRAM PC-133 [buy]
Memory Slots: 2
Slot Maximum: 256 MB

iMac G3 (350, 400, 500, 600 MHz)
Maximum Memory: 1 GB
Memory Type: 168-pin DIMM SDRAM PC-133 [buy]
Memory Slots: 2
Slot Maximum: 512 MB

iMac G4 (700, 800 MHz)
Maximum Memory: 1 GB
Memory Type: 144-pin SODIMM SDRAM PC-133 [buy]
Memory Slots: 2
Slot Maximum: 512 MB

iMac G4 (1.00, 1.25 GHz)
Maximum Memory: 1 GB
Memory Type: 200-pin SODIMM DDR PC-2700 [buy]
Memory Slots: 1 (*Has DIMM slot that is not accessible)
Slot Maximum: 512 MB


iMac G5 (1.60, 1.80 GHz)
Maximum Memory: 2 GB
Memory Type: 184-pin DIMM DDR PC-3200 [buy]
Memory Slots: 2
Slot Maximum: 1 GB (Best to use pairs)

iMac G5 (1.9, 2.1 GHz)
Maximum Memory: 2.5 GB
Memory Type: 240-pin DIMM DDR2 PC2-4200 (533 MHz) [buy]
Memory Slots: 1 (512 MB not removable)
Slot Maximum: 2 GB

iMac Intel Core Duo
Maximum Memory: 2 GB
Memory Type: 200-pin SODIMM DDR2 PC2-5300 [buy]
Memory Slots: 2
Slot Maximum: 1 GB

iMac Intel Core 2 Duo (1.83 GHz)
Maximum Memory: 2 GB
Memory Type: 200-pin SODIMM DDR2 PC2-5300 [buy]
Memory Slots: 2
Slot Maximum: 1 GB

iMac Intel Core 2 Duo (Late 2006)
Maximum Memory: 3 GB
Memory Type: 200-pin SODIMM DDR2 PC2-5300 [buy]
Memory Slots: 2
Slot Maximum: 2 GB

iMac Intel Core 2 Duo (Mid 2007)
Maximum Memory: 4 GB
Memory Type: 200-pin SODIMM DDR2 PC2-5300 [buy]
Memory Slots: 2
Slot Maximum: 2 GB

iMac Intel Core 2 Duo (Early 2008)
Maximum Memory: 4 GB
Memory Type: 200-pin SODIMM DDR2 PC2-6400 [buy]
Memory Slots: 2
Slot Maximum: 2 GB

iMac Intel Core 2 Duo (Early 2009)
Maximum Memory: 8 GB
Memory Type: 204-pin SODIMM DDR3 PC3-8500 [buy]
Memory Slots: 2
Slot Maximum: 4 GB

iMac (21.5-inch and 27-inch, Late 2009)
Maximum Memory: 16 GB
Memory Type: 204-pin SODIMM DDR3 PC3-8500 (1066 MHz) [buy]
Memory Slots: 4
Slot Maximum: 4 GB

iMac (21.5-inch and 27-inch, Mid 2010 and Mid 2011)
Maximum Memory: 16 GB
Memory Type: 204-pin SODIMM DDR3 PC3-10600 (1333 MHz) [buy]
Memory Slots: 4
Slot Maximum: 4 GB

iMac (27-inch, Late 2012 to Mid 2015)
Maximum Memory: 32 GB
Memory Type: 204-pin SODIMM DDR3 PC3-12800 (1600 MHz) [buy]
Memory Slots: 4
Slot Maximum: 8 GB

iMac (Retina 5K, 27-inch, Late 2015)
Maximum Memory: 32 GB
Memory Type: 204-pin SODIMM DDR3 PC3-14900 (1867 MHz) [buy]
Memory Slots: 4
Slot Maximum: 8 GB

iMac (Retina 5K, 27-inch, 2017)
Maximum Memory: 64 GB
Memory Type: 260-pin SODIMM DDR4 PC4-19200 (2400 MHz) [buy]
Memory Slots: 4
Slot Maximum: 16 GB

iMac (Retina 5K, 27-inch, 2019)
Maximum Memory: 64 GB
Memory Type: 260-pin SODIMM DDR4 PC4-21333 (2666 MHz) [buy]
Memory Slots: 4
Slot Maximum: 16 GB

iMac (Retina 5K, 27-inch, 2020)
Maximum Memory: 128 GB
Memory Type: 260-pin SODIMM DDR4 PC4-21333 (2666 MHz) [buy]
Memory Slots: 4
Slot Maximum: 32 GB

The 21.5-inch iMac models from Late 2012 to 2019 don't have memory you can replace yourself: Apple says to use an Apple Authorized Service Provider, and the 21.5-inch Late 2015 models can't be upgraded at all. iMac models with Apple silicon have memory built into the chip, so it's chosen when you buy. Apple's memory guide for every model: Install memory in an iMac.