If you want a single number. Go calculate your expected expenses (it's good to track current expenses, then add on provisions for health insurance, travel, car replacement, new roof, etc.).
Highly overlooked thing.
Always take into account the housing upkeep and maintenance as they usually end up as 'surprise' costs for items and labor upcharging as 'emergency', but need to allocate projected funds every year.
Roof replacement
House paint job
Water heater
Refrigerator
Oven or microwave
Random plumbing in kitchen or bathroom - those rubber grommets / o-rings wear thin or crack
Washer / dryer
Garage door openers
Furnace / HVAC
Backyard grill, fire pit, or entertainment items
Patio stones
Tree trimming or root created damage
Yard bark or beautification
Sprinkler system
Septic or underground piping
Fence panels and painting/staining
Deck plank refresh
Replace the lawn mower or other typical tools.
Bound to be something every year so budget for them. Best to systematically replace items when you got the coin and know things age.
Know you are going to retire within 5 years? Start a phased replacement/upgrade on major appliances while you got the paycheck.