Does kicker count toward the converted mana cost of a spell when it's on the stack?

A spell's mana value (formerly called converted mana cost) is always calculated from the mana cost printed in the card's upper-right corner, regardless of any additional or optional costs paid to cast it. Kicker is an optional additional cost defined under CR 702.33, and paying it does not change what is printed in the mana cost.

CR 202.3 states that a spell's mana value on the stack is determined by its mana cost, period. Additional costs — including kicker, entwine, escalate, and similar mechanics — are explicitly excluded from this calculation. So a kicked Rite of Replication (mana cost {4}{U}) still has a mana value of 5 on the stack, not 14.

This matters in several practical contexts: effects that counter spells with mana value 3 or less, cards like Condescend that interact with mana value, or replacement effects that care about the spell's cost. None of those count the kicker payment.

Concrete example: You cast Goblin Bushwhacker ({R}, mana value 1) with its kicker cost of {R} paid, spending {R}{R} total. While it is on the stack, its mana value is still 1. An opponent's Spell Snare (counters a spell with mana value 2) cannot counter it, because its mana value remains 1 despite the extra mana spent.

Summary: kicker is an additional cost (CR 702.33a), and additional costs never modify a spell's mana value (CR 202.3). The printed mana cost is the only thing that counts.