Public transport
Use your realistic ticket strategy: season ticket, flexi ticket, daily tickets or advance fares. Add connecting transport where it is genuinely part of the commute.
Driving
At minimum include incremental fuel, parking and tolls. For a fuller vehicle-cost view you can also estimate mileage-related wear, servicing and depreciation, but be careful not to double-count fixed costs you would incur even without the commute.
Office-day spending
Meals, coffee or childcare changes can matter if they are specifically caused by the office day. Small daily amounts become significant when annualised.
Time
Record door-to-door travel in both directions. The annual hours number is useful even if you choose not to assign it a cash value.
Use working weeks, not 52 automatically
Holiday, bank holidays, sickness and remote weeks mean most commuters travel fewer than 52 full working weeks. The site defaults to 47 so you can adjust it to your own pattern.