- "Have either of you boys heard of... the Calculator?"
- —Damien Darhk to Danny Brickwell and Michael Amar[src]
Noah Kuttler, alias "The Calculator", is a fugitive cyber-criminal, the ex-husband of Donna Smoak, and the father of Felicity Smoak. A computer genius and an intellectual, he is described as a man of great intelligence, having had conversations that even his wife did not understand.
Leaving his family
When his daughter Felicity was seven, he was said to abandon her and his wife, Donna, to avoid going to prison. In reality, Noah didn't have much choice, as Donna decided not to gamble with fate on the chance that her husband could reform from his criminal ways, and decided to escape from Noah, disappearing from his life. 
Coercing Roy Harper
While Roy was living under a new identity, Noah discovered Roy's secret. He then blackmailed Roy into helping him, telling him he would reveal his identity. To watch Roy's every move, the man had Roy put on a lens in his right eye. But then Oliver saved him.
Kuttler was contacted by an unknown employer and hired to detonate a web nuke to take down Star City. He had Roy steal several parts to build this nuke. Team Arrow managed to free Roy from his influence. Felicity broke through his encryption code and he contacted Felicity, disguising his voice. Noah told Felicity his intention wasn't to take down the internet but a city.
Once a few mercenaries placed the device on site, Noah was contacted by Felicity. Noah teased her that he would blow up a subway and that the only way he could be stopped would be if the device was removed. Once Felicity installed a firewall, he told her it didn't matter because he could decode the firewall with ease. Noah decoded the firewall, but Roy destroyed the device before he could execute the web nuke. A virus was then installed on his computer to remove everything he had on Roy. 
Reuniting with Felicity
While Felicity made her presentation at Palmer Technologies, Noah watched. Noah applauded her presentation and complimented her to Oliver Queen. He then greeted his daughter after the presentation. 
While out to dinner with Felicity, Noah referred to her as "Overwatch", revealing his identity as the Calculator. He stated that they had a lot in common as they were both vigilante hackers. Noah claimed that he wanted to be in her life and to get to know her, even handing over a flash drive of some of his hacks as proof. Taking her mom's advice on not to get close to him because people don't change, Felicity set up a trap for Noah and learned he was only getting close to her to steal data from Palmer Technologies. Felicity later turned her father in to the SCPD, proclaiming that they were nothing alike as he was handcuffed and read his rights by Quentin Lance, who is now her mother's new boyfriend. 
Enemy of H.I.V.E.
After activating the reprogrammed Rubicon protocol, H.I.V.E. leader Damien Darhk believed that Noah was the only one able to hack Rubicon and foil his plans. He sent his men to execute him but Noah managed to escape and was finally rescued by Team Arrow. He along with Felicity broke into Palmer Technologies to steal a processor needed to hack into Rubicon. Although they managed to copy only 90% of the processor, he extrapolated the design to complete it. Working with Felicity he was able to stop all but one nuke, all the while being hunted by Damien Darhk's underlings: Danny Brickwell and Michael Amar. He then took a bullet trying to save Felicity.  Noah survived the bullet and, after much arguing with his wife about their life together, returned to the mission and worked on subverting another H.I.V.E. attempt to get control over Rubicon through computer hacking, this time with the employ of Brother Eye leader Cooper Seldon. Assisted by Felicity and Curtis, the Calculator prevailed over Cooper's efforts, managing to overload the man's whole computer. Following this victory, Noah left the premises on request from Donna, who thought that he remained every bit as dangerous to their daughter as the day she took her away from him. 
As the Calculator, Noah is an opportunist criminal, with great disregard for the lives of others and no qualms with controlling and blackmailing people he has no love for, such as Roy Harper. He's a graceful loser, shown when he tried to re-connect with Felicity, impressed by the fact that she managed to outsmart him during the "web nuke" plot. Despite being an unrepentant criminal, Noah harbors great love for his family, agreeing to leave only after Donna's argument that not living together with a fugitive father would be better for their daughter, still, Noah was reluctant to leave, thinking that after everything that's happened, Felicity would be crushed to see him disappear from her life again. 
- Genius-level intellect: According to Donna, Felicity's intellect was inherited from her father, Noah. This is proven when he was the only hacker better than Felicity. His intellectual skills surpassed those even of Felicity's hence making him one of the best hackers and one of the most intelligent individuals in the multiverse.
- Computer specialist/Master computer hacker: Noah is a highly skilled computer hacker, his hacking skills surpassed those even of Felicity's. His skills are so advanced that even Damien Darhk acknowledged Noah as the only one able to hack Rubicon and foil his plans. 
- IR Burst Receiver: Noah left behind an incredibly advanced device at Palmer Tech to steal it's data. This was collected and turned off by his daughter.
Behind the scenes
- In the DC comics, Noah Kuttler, the Calculator, started off as a criminal whose outfit was an actual calculator, claiming he could genuinely calculate the formulas for victory. However, after hearing about Oracle, Noah became an info broker to super villains, charging money per question and setting up jobs for other criminals. Also in the comics, Noah also has daughter and a son who are named Wendy and Marvin Kuttler/White who are also based off the twins characters from the Super Friends animated TV show.