In at 10:20 AM, out at 1:45 PM: $15.50 on this sample rate sign
A parking fee is built from the minutes between entry and exit and the garage's rate sign: free time first, then a first-period charge, then a charge for every additional unit. Take a garage that lets you leave free within 30 minutes (those 30 minutes are subtracted), charges $3.00 for the first 30 billable minutes and $2.50 for each additional 30 minutes or part of one. Parking from 10:20 AM to 1:45 PM is 3 hours 25 minutes (205 minutes). Subtract the 30 free minutes and 175 minutes are billable: $3.00 for the first 30, plus 145 more minutes rounded up to 5 units of 30 minutes, $12.50, for a total of $15.50.
On the same sign, leaving at 1:50 PM costs the same $15.50, and 1:51 PM costs $18.00 because a sixth unit starts. Fees climb in steps, so leaving a few minutes earlier can save a whole unit. Drag the fee-step chart above the calculator, or tap a row under "If you leave by", to see the fee for each exit time.
When it pays to run the numbers before you leave
- You were given free minutes: check whether they are subtracted from the stay or only apply if you leave inside the window. The two readings differ by $2.50, one extra unit, on a 3-hour stay (see the table below).
- A short errand: if a garage has a grace period, one minute over it can change the fee from $0.00 to a full first-period charge.
- A multi-day airport trip: a daily maximum restarts on a schedule the garage sets, so once you know it you can budget the last partial day before you fly.
- A validated stay: if a business stamps your ticket for a fixed number of free hours, enter those hours as free time to see what is left to pay.
How the fee is calculated
- Count the minutes from entry to exit. If you stayed past midnight, set the exit date to the next day.
- Apply free time. "Subtract" removes the free minutes from the start of the stay and charges the rest. "All or nothing" gives $0.00 only if you leave within the free time; one minute over and you pay from the moment you entered.
- If the billable time is no longer than the first period, you pay the first-period charge once.
- Time beyond the first period is divided into additional units, always rounded up. With 30-minute units, 1 extra minute counts as one full unit.
- If there is a maximum, the stay is cut into 24-hour periods after entry (or calendar days). Each period restarts the rate sign from the beginning and is capped at the maximum. Free time applies only to the start of the stay.
- A percentage discount is taken off the total and the result is rounded down to the cent.
How the fee changes with the exit time
The table uses the sample rate sign from the intro, entering at 10:20 AM, with the two ways garages treat free time.
| Exit | Time parked | Subtract | All or nothing |
|---|---|---|---|
| 10:50 AM | 30 min | $0.00 | $0.00 |
| 10:51 AM | 31 min | $3.00 | $5.50 |
| 11:20 AM | 1 h | $3.00 | $5.50 |
| 11:21 AM | 1 h 1 min | $5.50 | $8.00 |
| 11:51 AM | 1 h 31 min | $8.00 | $10.50 |
| 12:50 PM | 2 h 30 min | $10.50 | $13.00 |
| 1:45 PM | 3 h 25 min | $15.50 | $18.00 |
| 1:50 PM | 3 h 30 min | $15.50 | $18.00 |
| 1:51 PM | 3 h 31 min | $18.00 | $20.50 |
At 10:51 AM, "subtract" bills only 1 minute and charges the $3.00 first period, while "all or nothing" bills all 31 minutes: $3.00 plus one $2.50 unit. For the same 205 minutes the two methods are $2.50 apart. If a sign only says "first 30 minutes free", ask the attendant which one applies.
Daily maximum: 24 hours after entry or calendar day
A daily maximum keeps a long stay from growing without limit, but garages word it differently. Some count 24 hours from the moment you entered; others cut at midnight. The airport pages in the sources below say "daily maximum" without defining the day, so the sign at the garage or the operator is the only way to know. This calculator can apply either rule. The table uses $2.00 per 30 minutes, a $28.00 daily maximum and no free time.
| Stay | 24 h after entry | Each calendar day |
|---|---|---|
| 9:00 AM to 6:00 PM (9 h) | $28.00 | $28.00 |
| 9:00 PM to 9:00 AM next day (12 h) | $28.00 | $40.00 |
| 6:00 PM to 8:00 AM next day (14 h) | $28.00 | $52.00 |
| 9:00 AM to 11:30 AM next day (26 h 30 min) | $38.00 | $56.00 |
| 9:00 AM to 9:00 AM two days later (48 h) | $56.00 | $84.00 |
The 9:00 PM to 9:00 AM stay shows the gap: split at midnight it is a 3-hour piece ($12.00) plus a 9-hour piece that reaches the $28.00 cap, which comes to $40.00. If you cannot tell which rule applies, budget with the higher figure.
A published airport rate sign: Sonoma County Airport (STS)
The Charles M. Schulz Sonoma County Airport states, for rates effective July 1, 2026: "The first 30 minutes of parking in the Short Term Parking Lot are free" and "Fees are $2 per 30 minutes with an $28 daily maximum." It adds that the free 30 minutes applies only on the first day, and that each later day is subject to the posted daily maximum. In the calculator that is 30 free minutes ("Subtract"), no first period, $2.00 every 30 minutes, and a $28.00 maximum per 24 hours. The "Airport, 3 days" example button is this sign.
| Time parked | Fee | Note |
|---|---|---|
| 30 min | $0.00 | Inside the free 30 minutes |
| 31 min | $2.00 | 1 billable minute rounds up to one unit |
| 2 h | $6.00 | 90 billable minutes, 3 units |
| 5 h | $18.00 | 9 units |
| 7 h 1 min to 24 h | $28.00 | Maximum reached |
| 25 h | $32.00 | $28.00 + 1 h in the next period, $4.00 (no second free time) |
| 50 h 30 min | $66.00 | $28.00 × 2 + 2 h 30 min, $10.00 |
| 72 h | $84.00 | $28.00 × 3 |
The airport does not say whether "day" means 24 hours or a calendar day. Entering at 7:40 AM and leaving two days later at 10:10 AM gives $66.00 on a 24-hour basis and $84.00 if each calendar day is capped separately. The page also does not say whether a partial 30 minutes is rounded up, so the calculator assumes it is. Another airport, Bismarck, lists a similar structure for its short-term lot: first 30 minutes free, $1 for each half hour and a $14 daily maximum, with rates effective June 1, 2023.
Validation and free hours
Some businesses reduce parking cost by validating your ticket. The Sonoma County Airport page is one official example:
Patrons of authorized pre-security concessions are entitled to up to two (2) hours of free parking total with validation.Charles M. Schulz Sonoma County Airport, Parking page, rates effective July 1, 2026 · read 2026-10-20
The page does not say whether those two hours replace the 30 free minutes or how a longer stay is billed afterward. The "2 h validated" example assumes the two hours are subtracted from the stay, with the same $2.00 per 30 minutes and $28.00 maximum. Entering at 9:00 AM and leaving at 12:10 PM (3 h 10 min), 70 minutes are billable, 3 units: $6.00. Without validation, only 30 minutes are free, 160 minutes are billable, 6 units: $12.00. Confirm with the cashier how your validation is applied.
Common mistakes
- Leaving the exit date unchanged after midnight: entering at 11:50 PM and leaving at 12:20 AM is 30 minutes only if the exit date is the next day. Otherwise the calculator reports that the exit is earlier than the entry.
- Treating a grace period as subtracted free time: on the sample sign this understates a 205-minute stay by $2.50.
- Assuming "daily" means calendar day: if the garage counts 24 hours from entry, an overnight stay comes out far cheaper than the date rule suggests.
- Prorating the unit price: $2.00 per 30 minutes is not about 6.7 cents a minute. This calculator charges a partial unit as a whole one; confirm that on the sign.
- Reading the payment time as the exit time: some garages add a charge if you do not leave within a set time after paying.
Limits
- The calculator takes one rate sign. Garages that price by tiers (for example, $4 for the first hour, $8 up to two hours, then $5 each additional hour, as Harry Reid International Airport lists for its short-term parking) cannot be entered exactly as one first period plus a repeating unit.
- Different weekday and weekend maximums, overnight flat rates and time-of-day pricing must be calculated in separate pieces.
- The maximum repeats in every period. A garage that applies the maximum only once in the first 24 hours can give a different total from the second day on.
- The calendar-day option restarts the rate sign at midnight. A garage that keeps counting a unit across midnight may differ by one unit.
- The discount is rounded down to the cent. Amounts shown are the rate-sign fee only; taxes, reservation fees and card-processing fees are not added.
- Times use this device's time zone and elapsed time is real time, so a daylight saving change is handled. One stay is calculated up to 366 days.
As of The Sonoma County Airport, Bismarck Airport and Harry Reid International Airport pages were read on 2026-10-20. Sonoma County states its rates are effective July 1, 2026; Bismarck states June 1, 2023, and Harry Reid's page shows no date. The sample rate sign in the intro, the first two tables and the "30 min free + hourly" example are illustrative rates, not a real garage's.
Sources
- 01Charles M. Schulz Sonoma County Airport: Parking"The first 30 minutes of parking in the Short Term Parking Lot are free", "$2 per 30 minutes with an $28 daily maximum", free time first day only, two hours free with concession validation, rates effective July 1, 2026 (read 2026-10-20)
- 02Bismarck Airport: Parking InformationShort-term lot: first 30 minutes free, each half hour $1, daily maximum $14, rates effective June 1, 2023 (read 2026-10-20)
- 03Harry Reid International Airport: ParkingShort term: 0 to 1 hour $4, 1 to 2 hours $8, each additional hour $5, daily maximum $38 (read 2026-10-20)
FAQ
What does parking from 10:20 AM to 1:45 PM cost?
On a sign with 30 free minutes subtracted, $3.00 for the first 30 minutes and $2.50 per additional 30 minutes, 205 minutes parked leaves 175 billable and the fee is $15.50. Leaving at 1:50 PM costs the same, and 1:51 PM costs $18.00.
Are free minutes subtracted from the time parked?
It depends on the garage. If they are subtracted, the 205-minute stay above costs $15.50. If the free time is all or nothing, staying past it means paying from the moment you entered, and the same stay costs $18.00.
What is the difference between free time and a grace period?
A grace period is a window in which leaving costs nothing. Choosing All or nothing in this calculator charges the whole stay once the grace time is passed. Sonoma County Airport states that the first 30 minutes in its short-term lot are free; with $2.00 per 30 minutes, a 31-minute stay costs $2.00 if the free time is subtracted and $4.00 with All or nothing.
Does one minute over a unit cost a full unit?
This calculator rounds up to the unit. On the sample sign, leaving at 1:50 PM costs $15.50 and one minute later costs $18.00. A garage that bills by the minute could give a different amount.
Is a daily maximum counted per 24 hours or per calendar day?
It depends on the garage. With $2.00 per 30 minutes and a $28.00 maximum, parking from 9:00 AM to 11:30 AM the next day costs $38.00 on a 24-hour basis and $56.00 if each calendar day is capped separately.
How is a multi-day airport stay calculated?
Each 24-hour period restarts the rate sign and is capped at the maximum. With the Sonoma County Airport short-term sign (30 free minutes on the first day, $2.00 per 30 minutes, $28.00 maximum), 50 hours 30 minutes costs $66.00 on a 24-hour basis.
How do I enter validated free parking?
Enter the validated hours as free time. Sonoma County Airport says patrons of authorized pre-security concessions get up to two hours free with validation. Parking 3 hours 10 minutes with 2 hours subtracted at $2.00 per 30 minutes costs $6.00, against $12.00 with only the 30 free minutes.
How do I enter a stay that crosses midnight?
Enter the entry date as that day and the exit date as the next day. Entering at 11:50 PM and leaving at 12:20 AM is then a 30-minute stay. If you leave the exit date unchanged, the calculator reports that the exit is earlier than the entry.