Many also admit they struggle to name their other half’s job title, favourite colour and best friend.
And one in 20 can’t remember her birthday, the year they were born or their wedding anniversary.
Not surprisingly then, their spouse’s favourite flowers and the location of their first date also leave men scratching their heads.
A spokesman for online luxury florists Bloom & Wild, which commissioned the research, said: “Things you should notice every day such as how they take their tea or coffee or even their eye colour seem to leave many men stumped.
“This could spell disaster when it comes to buying gifts. If you don’t know their favourite things, such as flowers or colours, you could end up making the wrong decision, undoing any good effect the surprise a gift may have.”
The OnePoll.com survey of 2,000 men in a relationship found almost one in ten men can’t be sure what colour eyes their lady has, without looking.
Four in ten have no idea what their other half’s favourite colour is while a third couldn’t tell you what her job title is.
Almost half are stumped when it comes to their wife or girlfriend’s bra size, with one in five also admitting they don’t know what clothes size they wear.
Their lady’s place of birth (14 per cent), whether or not they have any allergies (8 per cent) and the names of their best friends also leaves many men floundering.
More than one in three guys even admitted they couldn’t say when he and she first got together and another 17 per cent wouldn’t be able to recall the location of the first date.
One in twenty even owned up to not knowing the date of their wedding anniversary.
The study also found four in ten men have no idea what her favourite flowers are, with 12 per cent buying the wrong flowers as a result.