Short rounds, a Daily Challenge and 1,900+ questions across 13 topics, with an explanation and links to sources after every answer. Stop guessing what really matters.
Open the Quiz tab in Decarbonr, the carbon footprint app for iPhone. The quiz is included in Decarbonr's subscription.
Which of the following has the highest carbon footprint per kilogram?
Tap an answer to see the explanation.
Beef from a dedicated beef herd averages about 99 kg CO₂e per kilogram, against about 12 for pork, 10 for chicken and 3 for tofu.
Source: Poore & Nemecek (2018), via Our World in Data
Is a long-haul flight worse than a year of driving? Does recycling outweigh what is on your plate? The quiz turns questions like these into short rounds, explains every answer and links to sources for its topic, so you can check the figures yourself.
All of this is in the Quiz tab of Decarbonr.
Seven questions, the same for everyone each day. Play on consecutive days to build your streak.
Adult, Family-friendly and Kids, each written for a different reading level and spread across 13 topics.
Your accuracy in each topic shows where you are sharp and where you have room to grow.
Bronze, silver and gold badges for streaks, perfect rounds, milestones and trying every pack.
Earn XP per correct answer; climb seven ranks from Seedling to Planet Champion.
Two players take turns on one phone for a quick head-to-head with a friend, a parent or a classmate.
After each round, go back over every question with the right answer and its explanation.
Every answer comes with a plain-language explanation and two or three links to sources for its topic.
XP, streaks and achievements are stored on your phone. No account needed to play.
Turn a finished round into an image card to share with friends.
Each answer screen links to sources for its topic, so you can read the figures where they come from. Below are eight of the institutions the quiz links to.
The IPCC's Sixth Assessment Report (2021–2023) is the reference assessment of climate science, impacts and mitigation. The quiz links its Synthesis Report and its chapters on transport, agriculture and land use, buildings and climate policy.
IPCC (2023). AR6 Synthesis Report: Climate Change 2023.
NASA's climate change pages follow carbon dioxide, global temperature, sea level and ice from satellite and ground measurements. They are linked from the climate-science questions.
NASA Science. "Climate Change". science.nasa.gov/climate-change.
The IEA's analysis of transport, buildings, heat pumps, data centres and streaming video is linked from the questions on those topics.
IEA (2022). The Future of Heat Pumps.
Our World in Data's pages on the footprint of food and travel, on CO₂ and greenhouse gas emissions and on water use are linked from the food, transport, water and carbon-accounting questions.
Ritchie, H., Roser, M. & Rosado, P. (2024). "CO₂ and Greenhouse Gas Emissions". OurWorldInData.org.
The UN Food and Agriculture Organization's work on climate change, food loss and food waste is linked from the food questions.
FAO (2011). "Global food losses and food waste: Extent, causes and prevention".
The GHG Protocol's Corporate Standard and Scope 3 Standard are linked from the questions on business emissions and carbon accounting.
WRI/WBCSD (2015). The Greenhouse Gas Protocol: Corporate Standard (revised edition).
The US Environmental Protection Agency's pages on greenhouse gases, waste and recycling, composting and saving water are linked from the waste, water, shopping and carbon-accounting questions.
US EPA. "Overview of Greenhouse Gases". epa.gov/ghgemissions.
NOAA's Climate.gov explains how much carbon dioxide is in the atmosphere and why it keeps rising. It is linked from the climate-science questions.
Lindsey, R. "Climate Change: Atmospheric Carbon Dioxide". NOAA Climate.gov.
Other linked sources include the UNFCCC, the ICVCM, ENERGY STAR, fueleconomy.gov and the Ellen MacArthur Foundation.
Download Decarbonr from the App Store, open the Quiz tab and pick the Adult, Family or Kids pack.
Seven questions, ~3 minutes. The same set for everyone, so you can compare with friends.
Come back the next day to grow your streak, earn XP and unlock achievements.
Decarbonr estimates the carbon footprint of what you eat, how you travel and how you live, and adds it up to one number a day. The Carbon Footprint Quiz is a tab in the same app, so what you learn sits next to what you log.
Photograph a meal or scan a product barcode to get an estimate of its CO₂e. Scanning is part of the optional AI Features plan.
Add trips by car, train, bus or plane and see an estimate of the CO₂e of each one. City names you type are looked up with Apple Maps.
Food, travel, home energy and more add up to one daily CO₂e estimate, shown against the daily goal you set.
The Daily Challenge, three packs, answer review and sourced explanations are all in the Quiz tab.
Pick a language below to read this page in it. In Decarbonr, the quiz follows the app's language: every question is available in English and in the 43 other languages you can choose in the app.
Carbon Footprint Quiz is part of Decarbonr, the carbon footprint app for iPhone. Requires iOS 17.6 or later.
On a computer? Scan the code with your iPhone camera to open Decarbonr on the App Store.