Put his litter box on your porch, along with an article of clothing with your scent on it. Cats have a wonderful sense of smell and will come to those items. Leave a window cracked nearby so that you can hear him. Post pictures around the neighborhood and on doors. Ask neighbors to keep an eye out and to check garages and sheds. Cats hide, usually fairly close by. They tend to come out after dark, so look for him then. Call and rattle a treat can if he likes those. If you put food out, stay close by, because it will also attract other animals that might scare him away. Don't leave it out very long. Also, go in person to shelters and vets' offices, and leave a picture and phone number there. I hope you find him!
If he is indoor only I will add steps. Need to crack open the garage door or other access 24/7 to let him come back inside ASAP. Definitely close by and I’m sure has taken cover for warmth under a shed or crawl space for example. Need to get fliers. They always try to return to the exit they went usually and night and especially between 4-7 am. Keep an eye on that door and focus on luring with soft familiar calls from that door as often as possible. If you have an attached garage crack that just a bit with scent items inside and just outside both doors (garage and door he went out). Scent items are worn clothes of family, his bedding, your slept on sheets, litter box etc. They can hide so well nearby that it seems as though they have vanished. It’s a way of protecting themselves. Flier door to door in a 7 house radius of your home. That’s typically where they stay for quite some time. Even months. Baby monitor outside the door he escaped is always helpful to hear meows or scratching. Also see site for steps to finding an indoor only cat. There are also steps to outdoor access. Pet-trackerinc.org