This table shows a quick comparison between the characteristics of all the Arduino and Genuino boards.

Name	Processor	Operating/Input Voltage	CPU Speed	Analog In/Out	Digital IO/PWM	EEPROM [kB]	SRAM [kB]	Flash [kB]	USB	UART
101	Intel® Curie	3.3 V/ 7-12V	32MHz	6/0	14/4	–	24	196	Regular	–
Gemma	ATtiny85	3.3 V / 4-16 V	8 MHz	1/0	3/2	0.5	0.5	8	Micro	0
LilyPad	ATmega168V ATmega328P	2.7-5.5 V / 2.7-5.5 V	8MHz	6/0	14/6	0.512	1	16	–	–
LilyPad SimpleSnap	ATmega328P	2.7-5.5 V / 2.7-5.5 V	8 MHz	4/0	9/4	1	2	32	–	–
LilyPad USB	ATmega32U4	3.3 V / 3.8-5 V	8 MHz	4/0	9/4	1	2.5	32	Micro	–
Mega 2560	ATmega2560	5 V / 7-12 V	16 MHz	16/0	54/15	4	8	256	Regular	4
Micro	ATmega32U4	5 V / 7-12 V	16 MHz	12/0	20/7	1	2.5	32	Micro	1
MKR1000	SAMD21 Cortex-M0+	3.3 V/ 5V	48MHz	7/1	8/4	–	32	256	Micro	1
Pro	ATmega168 ATmega328P	3.3 V / 3.35-12 V 5 V / 5-12 V	8 MHz 16 MHz	6/0	14/6	0.512 1	1 2	16 32	–	1
Pro Mini	ATmega328P	3.3 V / 3.35-12 V 5 V / 5-12 V	8 MHz 16 MHz	6/0	14/6	1	2	32	–	1
Uno	ATmega328P	5 V / 7-12 V	16 MHz	6/0	14/6	1	2	32	Regular	1
Zero	ATSAMD21G18	3.3 V / 7-12 V	48 MHz	6/1	14/10	–	32	256	2 Micro	2
Due	ATSAM3X8E	3.3 V / 7-12 V	84 MHz	12/2	54/12	–	96	512	2 Micro	4
Esplora	ATmega32U4	5 V / 7-12 V	16 MHz	–	–	1	2.5	32	Micro	–
Ethernet	ATmega328P	5 V / 7-12 V	16 MHz	6/0	14/4	1	2	32	Regular	–
Leonardo	ATmega32U4	5 V / 7-12 V	16 MHz	12/0	20/7	1	2.5	32	Micro	1
Mega ADK	ATmega2560	5 V / 7-12 V	16 MHz	16/0	54/15	4	8	256	Regular	4
Mini	ATmega328P	5 V / 7-9 V	16 MHz	8/0	14/6	1	2	32	–	–
Nano	ATmega168 ATmega328P	5 V / 7-9 V	16 MHz	8/0	14/6	0.512 1	1 2	16 32	Mini	1
Yùn	ATmega32U4 AR9331 Linux	5 V	16 MHz 400MHz	12/0	20/7	1	2.5 16MB	32 64MB	Micro	1
Arduino Robot	ATmega32u4	5 V	16 MHz	6/0	20/6	1 KB (ATmega32u4)/ 512 Kbit (I2C)	2.5 KB (ATmega32u4)	32 KB (ATmega32u4) of which 4 KB used by bootloader	1	1
MKRZero	SAMD21 Cortex-M0+ 32bit low power ARM MCU	3.3 V	48 MHz	7 (ADC 8/10/12 bit)/1 (DAC 10 bit)	22/12	No	32 KB	256 KB	1	1

Arduino Retired boards specs

Name	Processor	Operating/Input Voltage	CPU Speed	Analog In/Out	Digital IO/PWM	EEPROM [kB]	SRAM [kB]	Flash [kB]	USB	UART
BT	ATmega328P	5 V / 2.5-12 V	16 MHz	6/0	14/6	1	2	32	–	1
Fio	ATmega328P	3.3 V / 3.7-7 V	8 MHz	8/0	14/6	1	2	32	Mini	1

Source: Arduino – Compare