CO2 Tracker
Track how you commute and eat each day, and see your estimated carbon footprint.
Weekly summary
This week
| Day | Mode of transport | Est. CO2e | Confirm |
|---|
Additional journeys (optional)
What did you eat this week?
Alcohol this week
Flying
Log each return flight you've taken (or plan to take) this year — date is optional, but a flight logged with a date over a year old stops counting toward your current yearly total automatically, so it stays representative of how you're flying now rather than growing forever. Counted per return trip, varying by destination continent and cabin class — rough DEFRA-style averages, not a real distance calculator.
Household energy
No bill submitted yet.
It's been over a year since this bill's end date — consider submitting an updated one below.
For the most accurate figure, submit a bill covering a whole year (e.g. 12 months) rather than a single month — that captures seasonal variation (more heating/lighting in winter) automatically, and you won't need to update it as often. Include everyday use like showering (if electric water heating), lighting, heating, and appliances. Uses a rough grid average of ~0.2 kg CO2e/kWh, split evenly across everyone in the household.
Optional — leave blank to skip. Uses a rough blended gas/oil factor of ~0.18 kg CO2e/kWh, split evenly across your household. Check a recent annual bill if unsure.
Optional — leave blank to skip. Check a recent water bill for this figure (usually shown in m³, sometimes called "cubic metres" or "units"). Uses a rough DEFRA-style combined supply + treatment factor of ~0.32 kg CO2e/m³, split evenly across your household.
Pets Optional
Uses rough average footprints of ~770 kg CO2e/yr per dog and ~310 kg CO2e/yr per cat — mostly driven by their (often meat-heavy) diet — split evenly across everyone in your household (the "People in your household" figure above), the same way home energy is, since a household's pets aren't really just one person's footprint. Answering either one counts the other as 0 if left blank.
Banking Optional
Uses MotherTree's bank carbon emissions league table, which estimates each UK bank's indirect footprint from financing fossil fuels, per £ of customer deposits held. Both the bank and a balance need answering for this to count — picking a bank without a balance (or vice versa) leaves it out of your total, same as any other optional field here.
Buying goods
Uses a rough blended average of ~10 kg CO2e per item — a T-shirt is much less, a coat or a pair of jeans much more.
This week
You and your accepted friends, ranked by this week's average kg CO2e per confirmed day so far, lowest first — not by raw total, so being behind on logging days doesn't make you look artificially better than someone who's kept every day up to date. The total and how many days you've confirmed (out of how many have happened so far this week) are shown next to each person's average. Add friends from the Account page.
Habits
Fully optional — pick one habit to focus on (eating, commuting, flying, or banking), ranked by whichever is the biggest part of your own footprint.
All-time weekly average
Average CO2e per week since each person started confirming weeks, lowest first. Includes a weekly-equivalent share of flights and home electricity (yearly figures from the Stats page, divided by 52), so it isn't just commute and food.
Everyone on the app
Anonymous, aggregate figures — never anyone's individual data or name. The averages below are across every account with at least one fully confirmed week; the total signups figure is every account ever created, active or not.
Total CO2 saved
Budget pace
To do
Tap an item to log it.
- Yesterday's commute
- Yesterday's meal
- Today's commute
- Today's meal
- Electricity per year
- Flights per year
✓ All done — nothing outstanding right now.
Your year, estimated
Compared to:
Rough, illustrative estimate.
Account
Profile
All targets are rough assumptions. Feel free to base your goals on any of them. Each covers your whole footprint - commute, food, flights, home energy, buying goods, and any optional extras you've answered - not just commute and food, so the Budget pace chart on Home (which now plots every domain) compares like for like.
Wasted food still carries the emissions it took to produce, so this scales up your food figures everywhere (This Week, Stats) to account for it — e.g. 10–30% waste means buying/producing about 25% more than you actually eat. Your goal colors the boxes on the History section: green at or under goal, amber a bit over, red well over.
Delete account
Permanently deletes your account and everything tied to it — your login, profile settings, every week you've logged, and your friend connections. This is different from “Reset all data” on the Data section, which only clears your data but keeps your account. Deleting your account cannot be undone
Settings
Vehicle Optional
If yes, adds a rough ~700 kg CO2e/yr for the car's own manufacturing footprint, amortized over an average ~14-year car lifetime — separate from the fuel/charging for trips you log elsewhere in the app.
Uses rough DEFRA-style factors: diesel ~0.171 kg CO2e/km (about the same as the blended average used if you leave this blank), hybrid ~0.111 kg CO2e/km, electric ~0.058 kg CO2e/km (using average UK grid intensity to charge it). Replaces the default car factor for both your logged commute days (whenever you pick "Car") and any Car-mode additional journeys you log on the This Week page.
Daily reminder
Only available in the iOS app, not the web version — local notifications need the native app to actually schedule them.
A single local notification, rescheduled on this device whenever you open the app — nothing is sent from a server, and it's always the same generic nudge, never your data. Stored on this device only, so you'll need to turn it back on if you reinstall the app or sign in elsewhere.
Baseline week
By default, the Weekly summary card on This Week measures you against a bottom-up UK average. Set a typical week from before you started tracking instead — useful if your habits were very different back then — and it'll compare against that going forward.
| Day | Mode of transport |
|---|
What did you usually eat?
Baseline weekly total: 0 kg CO2e
Pick one of your own tracked weeks to start from — you can still tweak individual days afterwards on the Custom week tab.
Your baseline is the UK average week — no custom data saved.
Country
Optional - "Prefer not to say" leaves it unanswered. Powers the "All Members" Leaderboard's country filter (only for people who've also turned on "Show me on the public leaderboard" under Data sharing) and the Home page's country-average comparison.
Data sharing
Off by default — nothing is shared unless you turn this on. If enabled, everything on this page and the Stats page becomes visible to the app developer except your bank/banking answers, which are always left out. Your name, email, and account are never included — the developer only ever sees the raw numbers (commute distance, diet mix, flights, home energy, heating, pets, water, etc.), not who they belong to.
Off by default. Turning this on makes your display name and this week's total kg CO2e visible to any signed-in user on the Leaderboard's "All Members" view (filterable by university/country) - unlike Friends, which only ever shows people you've both accepted. Nothing else about your data becomes visible.
Only visible signed in as the app owner — pulls every opted-in
user's data via a server-side check on your account email, same
data as the research_profiles/research_weeks
views in supabase/schema.sql. The Excel version loads
a small spreadsheet library on demand (only when you click it), and
splits the data into a "Profiles" and a "Weeks" sheet.
What this doesn't account for
- Travel beyond your logged commute: taxis/rideshare, buses, trains, ferries, cruises
- Diet + purchases beyond what's tracked: dairy, eggs, snacks, food miles, electronics, subscriptions, household waste
- Investments beyond your bank balance — stocks, funds, and pensions can carry their own financed-emissions footprint (will be available soon...)
- Your share of public services and infrastructure — roughly 3.3 tonnes CO2e/yr per person in the UK
Friends
Friends
Requests received
Requests sent
Your friends
Friends can see your weekly total on the Leaderboard once you've both accepted — never your day-by-day commute or diet detail.
History
Your weeks
Each box is one week (Mon–Sun). Tap a box to see the day-by-day breakdown.
Data
Your data
"Reset this week" clears just whichever week you last had open on This Week (this week or last week). "Reset all data" resets your weekly logs and profile settings (not your friends). Everything is stored in your account, synced across devices you sign in on.