Being early 40s I'm at a pretty unique age that I use imperial in metric mixed.
measurements I can do either, through prefer millimeters for small stuff under an inch.
Fluids depend on what it is, litres for paint, pints for milk, water, stock and beer, litres for fuel prices, miles for milage. Again I tend to default to metric for small stuff under a pint.
Weights, I tend to be mainly metric, but if buying loose stuff over the counter it's oz and lbs.
People... stones and a lbs, feet and inches. I can visualize a 6ft tall 14 stone bloke, but give it me in metric I'll need a moment to convert it.
I used to work an a hardware store and mixed systems were quite usual.
Can I have 2.4m of 3"X2"...
How many square meters of laminate floor do I need for a 12ft by 18ft room.
Have you got 4ft of M8 threaded bar.
8ft of 2.5mm T&E
... four candles please.