LivingSocial is set to run a campaign tomorrow offering half-price vouchers for five big Macs and five large orders of french fries from McDonald’s for $13, normally a $26 value, according to LivingSocial.

LivingSocial, which is partially owned by Amazon, said that this is their largest ever national fast food deal. As part of the deal, McDonald’s will be promoting LivingSocial at its restaurants and drive-thrus.

The number of vouchers available will be capped at 1 million. Rather than the standard LivingSocial system of providing printable vouchers, McDonald’s will be mailing vouchers to shoppers who purchase them, an in attempt to reduce fraud, according to the company.

LivingSocial members who purchased the McDonald’s vouchers will also receive a unique URL they can refer people to. If three people purchase the McDonald’s voucher through that link, the member who referred them will receive their voucher for free.

Breaking this down, the voucher would make the cost of a Big Mac and large fry $2.60, though that does not include a drink. Comparing the costs is a bit difficult, as prices vary quite a bit by location. But from our research, it appears that adding a medium drink to the Big Mac and large fry from the voucher will add about $1.30. So for $3.90, you have a meal with a drink. The regular price of a Big Mac combo – including the drink – is about $5.40 in Orlando, Florida. If a drink is added, the savings with the voucher is $1.50 per meal in our location, not including tax.