How can I tell how many bits my ssh key is?

Problem

I already created an ssh key for myself sometime in the past. I don't remember "how many bits" it is. How can I tell? I'm wondering because I'm using hosting at nearlyfreespeech.net and their faq says: Can I configure my ssh connection to use a public key? ... we will not install keys that have a length less than 1536 bits ... We prefer that you use a key at least 2048 bits in length, and if you are generating a new key, the recommended length is 4096 bits.