More than 40% of holidaymakers plan to change their travel plans as a result of the weak pound, a survey said.
Eight million people will also opt for a "staycation" in the UK rather than travelling abroad, as the pound now buys less euros and dollars than it did at the beginning of last year.
Research from travel insurance specialist Columbus Direct said 21 million people, or 41%, will travel to cheaper resorts, cut the time they spend aboard, or go on a self-catering holiday to save money.
Half of young people, between 18 and 34, said they would tighten their holiday budgets following Britain's June referendum vote to leave the European Union.
Holidaymakers travelling to New York or Florida will get £70 less when they buy £500 worth of US dollars compared to a year ago.
And those travelling from Paris to Athens will get £65 less for every £500 they exchange into euros, compared to last February.
Families on late skiing holidays in the Swiss Alps will have £88 less per £500 they change into Swiss francs than they did a year ago.
But travellers to Australia and Norway will lose the most in terms of holiday spending power.
Britons heading to Australia will be £111 worse off compared to February 2016, on every £500 they exchange into Australia dollars.
Visitors to Norway will have £103 less to spend per £500 they change into Norwegian krona than they did 12 months ago.
Columbus Direct head of brand Rob Thomas, said:"Anyone heading to Europe, the US and Australia especially will feel the pinch of less favourable exchange rates. We have enjoyed a strong currency for many years so the reduced strength of the pound is going to be noticeable for holidaymakers when it doesn't go as far as it used to."
Thomas added that setting a budget in advance and looking out for visitor passes in European cities that offer discounts on public transport and for museum visits were good ways to save cash.
However, the report did find a few places where the pound still stretches further. Those heading on long haul destinations to Japan, Mexico and Malaysia will get better value for their sterling compared to August 2016. The extra gains in local currencies would be worth between £22 and £27.
Columbus Direct said 2,005 people took part in the survey between 31 January and 3 February.