Treat your current ticket as if it was a 7-day Park Hopper.
Do the upgrade math for making it an 8-day Park Hopper.
Cost to Upgrade:
"Price bridging" for Upgrading Tickets has changed in some cases.
As it stands now, tickets purchased from stock issued before the
price increase of Feb. 12, 2017 (this is NOT necessarily related to the date that YOU purchased your tickets)
will be bridged only to the pre-increase price that Disney sold these tickets to the public.
That means:
There are currently
two different ticket upgrade scenarios:
1. To upgrade an "Old Price" Ticket:
If the ticket that you have, and want to upgrade, was purchased from an authorized ticket reseller from "old stock" or "leftover tickets" (a ticket minted BEFORE the Feb. 12 price increase,) THAT ticket will be price-bridged up to the full WDW on-line/phone-order price that was in place BEFORE Feb. 12, 2017. Even if you actually purchased your tickets after Feb. 12, if you bought
"leftover tickets" from the resellers older stock of tickets, they are considered to be tickets
minted before Feb. 12.
The on-line/phone-order price at which Disney sold these tickets to the public "before Feb. 12" will be the price subtracted from the CURRENT on-line/phone-order price of the new ticket to which you are upgrading.
That difference price will be the cost to upgrade.
2. To upgrade a "
New Price" Ticket:
If the ticket that you have, and want to upgrade, was purchased from an authorized ticket reseller from "current stock" (a ticket minted AFTER the Feb. 12 price increase,) THAT ticket will be price-bridged up to the full CURRENT WDW on-line/phone-order price.
That "current price" of your original ticket will be subtracted from the CURRENT on-line/phone-order price of the new ticket to which you are upgrading.
That difference price will be the cost to upgrade.
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Ticket on-line PRICES-PREVIOUS to Feb. 12, 2017 from an archived Allears page HERE.
Ticket on-line PRICES-CURRENT-Since Feb. 12, 2017 can be found on the WDW website HERE.