However, our network system is leveraging the learnings from the past 18 months, sharing best practices and skillfully executing by applying revenue growth management and working our supply chain levers to capitalize on the strengths of our brands and mitigate disruptions.
Highlights from this quarter include Coca-Cola Zero Sugar's new recipe has rolled out in more than 50 countries and has had accelerated growth in the last three months.
As an example, Wabi is seeing strong growth outside its home market of Latin America has more than 50 categories contributing meaningfully to its sales on the platform.
Our Q3 organic revenue was up 14% with concentrate shipments up 8% and price/mix up 6%.
Unit case growth was 6% with absolute unit cases ahead of 2019 levels for the first time this year and a sequential improvement versus the second quarter on a two-year basis.
Comparable gross margin for the quarter was up approximately 160 basis points versus prior year, driven by pricing in the market, positive mix and timing of shipments.
As a result, our comparable operating margin compressed by 40 basis points year over year, more than offsetting the flow-through from the strong top line.
Below operating income, we saw some leverage come through from the other income line and a lower tax rate for the quarter that was driven by our updated effective tax rate for the full year to 18.6% from 19.1% previously.
Putting all of this together, third-quarter comparable earnings per share of $0.65 was an increase of 18% year over year, including a three-point benefit from currency.
We also delivered strong year to date free cash flow of $8.5 billion.
We now expect to deliver organic revenue growth of 13% to 14%, which is at the high end of our previously provided range, and comparable earnings per share growth of 15% to 17% in 2021.
Our updated guidance for free cash flow of approximately $10.5 billion represent significant progress over the past few years and particularly during the COVID era.
This progress is further dimensionalized as follows: We expect to achieve this year a dividend payout ratio below our long-term target of 75% of free cash flow for the time since 2015.
We anticipate delivering another year of free cash flow conversion above 100%.
Four, our currency outlook continues to contemplate a tailwind of 1% to 2% to the top line and approximately 2% to 3% to comparable earnings per share in 2021 based on current spot rates and our hedge position.
Based on current rates and hedge position, we'd expect commodity inflation to have a mid-single-digit impact on our cost of goods sold in 2022.

Summary:
Our Q3 organic revenue was up 14% with concentrate shipments up 8% and price/mix up 6%.
Unit case growth was 6% with absolute unit cases ahead of 2019 levels for the first time this year and a sequential improvement versus the second quarter on a two-year basis.
Putting all of this together, third-quarter comparable earnings per share of $0.65 was an increase of 18% year over year, including a three-point benefit from currency.
We now expect to deliver organic revenue growth of 13% to 14%, which is at the high end of our previously provided range, and comparable earnings per share growth of 15% to 17% in 2021.
Our updated guidance for free cash flow of approximately $10.5 billion represent significant progress over the past few years and particularly during the COVID era.
This progress is further dimensionalized as follows: We expect to achieve this year a dividend payout ratio below our long-term target of 75% of free cash flow for the time since 2015.
We anticipate delivering another year of free cash flow conversion above 100%.
Four, our currency outlook continues to contemplate a tailwind of 1% to 2% to the top line and approximately 2% to 3% to comparable earnings per share in 2021 based on current spot rates and our hedge position.
Based on current rates and hedge position, we'd expect commodity inflation to have a mid-single-digit impact on our cost of goods sold in 2022.