Free calculator
What Time Should I Leave?
Calculate when to leave based on your arrival time, travel time, and extra buffer so you can get there on time.
Use this leave-time calculator to determine exactly when you should leave for a meeting, appointment, interview, class, or event based on your arrival time, travel time, and extra buffer.
Destination
Starting location
Arrival date
When do you need to arrive?
Travel mode
Extra buffer before arrival
Extra time for parking, walking in, or check-in (optional)
Travel time (minutes)
Enter a starting location and destination above for an automatic estimate.
Your leave time will appear here
Fill in your destination and arrival time, then click Calculate.
- •Real travel time based on traffic
- •Accounts for buffer and check-in time
- •Exact time to leave so you are not late
Stop doing this math every time
OnTimer connects to your calendar and automatically figures out when you need to leave — for meetings, appointments, and any event with a location. It alerts you at the right time, based on traffic, not a guess.
- ✓Time-to-Leave alerts based on real travel time and live traffic
- ✓Connects to Google Calendar and Microsoft Outlook
- ✓Works for any event with a location in your calendar
- ✓Stronger alerts that are harder to ignore than standard reminders
How this calculator works
The calculation is straightforward: start from when you need to arrive, then subtract travel time, your buffer, and any extra time you need for things like parking or checking in. The result is when you should walk out the door.
Travel time is estimated using Google's Routes API, which accounts for current and predicted traffic based on your departure time. Walking and transit times are also supported. If Google cannot estimate the route, you can enter the travel time manually.
The buffer is there because real life is not perfectly predictable. A 10-minute buffer costs you very little if everything goes smoothly, but saves you a lot of stress if something small goes wrong.
What to factor in before you leave
Traffic is the most variable factor. A route that takes 20 minutes at 10 AM might take 40 minutes at 5 PM on the same road. If your meeting is during peak hours, use a realistic estimate — not the best-case time from an earlier route check.
Parking and getting inside takes longer than most people expect. Finding a spot, walking to the building, waiting for an elevator — these steps easily add 5 to 15 minutes before you are actually in the room. The prep time field in the calculator is for exactly this.
Give yourself a buffer even when you think you do not need one. Unexpected things happen — a slow traffic light, a confusing entrance, a detour. A 10-minute buffer costs almost nothing when everything goes right, and buys you meaningful peace of mind when it does not.
Why standard reminders often are not enough
Calendar reminders are easy to set and easy to dismiss. Most people set them for 15 or 30 minutes before an event — but that is often not enough time to actually get ready, get out the door, and drive somewhere with any margin.
Standard reminders also do not account for travel time at all. A 15-minute reminder before a meeting 25 minutes away means you are already late before you leave.
OnTimer works differently. It calculates when you need to leave based on real travel time and traffic, then sends you a stronger, harder-to-ignore alert at that specific moment — not a generic 15 minutes before start.
Frequently asked questions
How do I calculate what time I should leave?+
Work backwards from when you need to arrive. Subtract your travel time, then subtract any buffer for unexpected delays, and any extra time you need for parking or checking in. The result is the latest you should walk out the door.
How much buffer should I add before a meeting or appointment?+
A 10-minute buffer handles most minor delays — a slow traffic light, a parking spot that takes a minute to find, or a brief wait in a lobby. For important appointments like job interviews or medical visits, 15–20 minutes is worth it.
Does travel time change based on when I leave?+
Yes. Traffic varies significantly by time of day and day of week. Leaving at 8 AM on a Tuesday is very different from leaving at 10 AM or on a Saturday. This calculator uses Google's live traffic data to estimate travel time based on when you plan to arrive.
What if I am taking transit or walking?+
Use the Transit or Walking mode in the calculator. Walking time is straightforward. Transit times depend on schedules and may have more variability — adding a few extra minutes of buffer is a good idea.
Can OnTimer automatically remind me when to leave?+
Yes. For any calendar event with a location, OnTimer calculates when you need to leave based on travel time and traffic, then sends you an alert at the right time. No manual calculation needed.
Get there on time, every time
Download OnTimer and get automatic leave-time reminders for meetings, appointments, and every event in your calendar.