How to Calculate 85% of a Sentence and Subtract Time Credit
“What is 85% of two years, and how much time is left after the credit?”
To calculate 85% of a sentence as a mathematical estimate, convert the sentence into days, multiply by 0.85, and subtract the credited days. That gives you a number to work with, but it does not establish which percentage applies or when someone will be released.
The math question and the legal question are different. Before relying on a result, confirm the applicable rules and the credited amount for the particular sentence.
The quick formula for an 85% estimate
For a hypothetical calculation using exactly 85%, the formula is:
Estimated remaining days = (sentence days × 0.85) − credited days
If you also want to subtract days served after sentencing, deduct those separately. Do not include any day that is already part of the credit you entered.
For example, using a 365-day year, a two-year sentence with 154 credited days produces this estimate:
(730 × 0.85) − 154 = 466.5 days
The AJB calculator would display that as 467 days, rounding the final result up to a whole day. That rounding is a display convention for this tool, not a statement of how a court or corrections agency must round its calculation.
An important Arizona distinction: 85% is not an exact rule for every sentence
Arizona’s earned-release-credit statute includes a rate of one credit day for every six days served, subject to eligibility and statutory limitations; it also provides a different rate for certain qualifying drug offenses (A.R.S. § 41-1604.07).
Mathematically, six days served plus one credit day makes seven days accounted for. Six divided by seven is approximately 85.714%, not exactly 85%.
That is why “multiply by 85%” should not be presented as a precise Arizona release-date calculation. The statute also addresses eligibility, forfeiture of credits, and release to supervision, so identifying a percentage alone does not resolve the full calculation (A.R.S. § 41-1604.07).
The examples below answer the arithmetic question: “What happens if I use exactly 85%?” They do not determine whether 85%, another percentage, or a different computation applies to a particular person.
How to calculate 85% of a two-year sentence
First, choose and disclose your conversion method. These examples use 365 days per year for a consistent approximation, not a calendar-based sentence computation.
For two years, the full sentence estimate is:
2 × 365 = 730 days
Next, apply the selected percentage:
730 × 0.85 = 620.5 days
Finally, subtract the assumed 154 days of credit:
620.5 − 154 = 466.5 days
That leaves 466.5 days in this mathematical estimate, displayed as 467 days after rounding up. It is not an official release date.
Why the order of the calculation matters
Subtracting the credit first produces a different answer. Compare these two expressions:
Percentage first, then credit: (730 × 0.85) − 154 = 466.5 days.
Credit first, then percentage: (730 − 154) × 0.85 = 489.6 days.
The AJB tool uses the first method for its percentage-based estimate. This explains the tool’s arithmetic; it is not a finding that this formula reproduces the official calculation for every sentence.
What is 85% of a 2.5-year sentence?
Using the same approximate conversion, 2.5 years equals 912.5 days. Multiplying by exactly 85% gives 775.625 days.
With 154 credited days, the calculation becomes:
(2.5 × 365 × 0.85) − 154 = 621.625 days
The calculator displays 622 days after rounding the final result up. You can enter that sentence as either 2.5 years or 2 years and 6 months.
Here is a comparison using the same assumptions:
2 years: 730 full sentence days; 620.5 days at 85%; 466.5 days after 154 credited days; rounded-up display: 467 days.
2.5 years: 912.5 full sentence days; 775.625 days at 85%; 621.625 days after 154 credited days; rounded-up display: 622 days.
3 years: 1,095 full sentence days; 930.75 days at 85%; 776.75 days after 154 credited days; rounded-up display: 777 days.
All three examples use 365-day years and an assumed 85% rate. None is a prediction of an actual release date.
How do you count days for time credit?
Counting the days between two dates is an arithmetic task. Deciding which days legally count as presentence credit is a separate issue.
For example, April 24 through September 25, 2026, can be counted two ways:
Elapsed days: September 25 minus April 24 equals 154 days.
Both dates included: Counting April 24 and September 25 equals 155 days.
That one-day difference explains why two people can count the same date range and get different answers. Neither date-counting option, by itself, determines the legally credited amount.
Arizona law provides credit for time actually spent in custody pursuant to the offense before sentencing for that offense, and requires the sentencing court to include the computation of credited time in the original or amended commitment order (A.R.S. § 13-712(B), (E)).
Start with the credit recorded in the sentencing paperwork rather than assuming that every day in a date range qualifies. If your count differs from the paperwork, ask your attorney to review the discrepancy.
Why years and months need an approximation warning
The calculator converts one year to 365 days and one month to 365 ÷ 12 days, or approximately 30.4167 days. This makes 2.5 years and 2 years plus 6 months produce the same estimate.
Actual calendar months are not all the same length, and leap years have an extra day. A calculation based on specific calendar dates can therefore differ from this standardized conversion.
Keep decimal values during the calculation rather than rounding each step. In these examples, only the final remaining total is rounded up for display.
The separate date-counting feature uses the actual dates entered, including leap days. It does not treat every month as 30.4167 days.
What should you check before relying on an estimate?
Use the result to organize questions, not to make release plans. Before relying on the number, confirm these details with counsel and the appropriate corrections agency:
Applicable rule: What earned-credit or other release provisions actually apply?
Presentence credit: Does the entered amount match the sentencing paperwork?
Additional time served: Are you subtracting only days not already included elsewhere?
Multiple sentences: Are there other terms or holds that need separate review?
Official dates: What does the agency’s calculation show, and how does it account for supervision?
Arizona’s statute specifically addresses release to consecutive terms and release to community supervision or probation, illustrating why finishing one arithmetic calculation does not necessarily mean someone is leaving custody or completing all obligations (A.R.S. § 41-1604.07(E), (I), (J)).
For more general explanations of sentencing and the criminal court process, visit the AJB Law Firm Reference Library. For help with a specific Arizona criminal matter, learn about AJB’s criminal-defense practice.
Use the AJB Sentence Time Estimate Calculator
If you want to compare several sentence lengths without repeating the arithmetic, the AJB Sentence Time Estimate Calculator is available for $12, paid once. It provides a mathematical breakdown, not a verified Arizona release calculation.
Use it to enter a sentence length, select a percentage, subtract credited days, count between dates, and compare scenarios. You can also print the estimate or save a text summary with the assumptions included.
You do not need to enter a name or case number into the calculator. A separate member account is used for purchase and access.
Get one-time access to the AJB Sentence Time Estimate Calculator for $12. Confirm the applicable legal rules and official calculation before relying on any result.
Frequently asked questions
Is 85% of two years 620.5 days?
Yes, if you use a 365-day year: 2 × 365 × 0.85 = 620.5 days. That is an arithmetic result before subtracting credit, not a determination that exactly 85% applies.
Does time credit come off before or after the percentage?
In the AJB calculator’s simplified model, the percentage is applied first, then credited days are subtracted. Confirm the actual sentence-computation method separately rather than treating the model as a legal rule.
Is presentence credit the same as earned release credit?
No. Arizona addresses custody credit before sentencing in A.R.S. § 13-712, while earned release credits have separate eligibility and accrual provisions in A.R.S. § 41-1604.07.
What if the calculator says zero days remain?
Zero means the entered deductions meet or exceed the selected mathematical target. It does not determine that someone is legally entitled to release.
Does buying the calculator include legal advice?
No. The purchase provides access to an educational calculation tool, not a consultation, case review, or attorney-client relationship.
This article is general educational information, not legal advice for a particular case. Neither the article nor the calculator establishes release eligibility or an official release date.
