I’ve done similar posts before comparing the larger Hairy Woodpecker with the smaller Downy Woodpecker. But I’ll repeat the lesson as I captured them both on a homemade birdfeeder during Thursday’s snowstorm.
The hairy is larger overall, but without a reference it’s tough to tell strictly by size. To really determine the species, check out the bill. The hairy has a much more substantial bill. Females of each species are shown.