How long you can really float a balance, when to apply, and what to do before the promo expires.
What you're actually getting
A 0% APR card gives you a fixed runway — usually 12 to 21 months — to pay down a balance with no interest. The clock starts when the transfer posts, not when you apply.
How long can you really float?
That depends on your monthly budget vs the balance. Use the 0% APR Runway Planner to find out the latest you can apply, the required monthly payment, and what happens to whatever's left when the promo ends.
The exit plan
If you'll have a balance when the promo ends, pre-decide your move: a second transfer, a personal loan, or a more aggressive payment. Run the Monthly Payment Calculator against the post-promo APR to know your "rescue payment" before you need it.