Patent term adjustment (PTA) restores days of patent term lost to USPTO processing delays, extending a patent’s effective life beyond the standard 20 years from filing. For commercially significant patents, every additional day of term can have material value. This calculator sums the three statutory delay categories under 35 U.S.C. 154(b), removes overlap, and subtracts applicant delay to estimate the net PTA days.
The three delay categories
A-delay — USPTO failure to meet timeliness requirements
A-delay accrues whenever the USPTO fails to act within its statutory deadlines at specific prosecution milestones:
| Milestone | Statutory deadline | A-delay trigger |
|---|---|---|
| First Office Action | 14 months from filing date | Each day past 14 months |
| Response to reply/appeal | 4 months from applicant’s reply | Each day past 4 months |
| Action after Board decision | 4 months after Board decision | Each day past 4 months |
| Issuance after fee payment | 4 months after issue fee paid | Each day past 4 months |
Each of these is tracked independently. A-delay for one milestone does not offset or cap A-delay at another.
B-delay — failure to issue within three years
B-delay accrues for every day the patent issues after the third anniversary of the actual filing date (not the priority date). This is the most common source of PTA in lengthy prosecutions, since many utility patents take more than three years to issue.
B-delay days = max(0, issue date − (filing date + 3 years))Unlike A-delay, B-delay is calculated in a single block from the three-year mark to issuance.
C-delay — interference, secrecy, and appeals
C-delay covers three specific categories:
- Days consumed by an interference or derivation proceeding
- Days the application was under a government secrecy order
- Days consumed by a successful appeal to the Board or a federal court
C-delay does not apply to all ex parte appeals — only those where the applicant ultimately prevails.
The two mandatory reductions
Overlap
If the same calendar days qualify as both A-delay and B-delay (or any other combination), they are counted only once under 35 U.S.C. 154(b)(2)(A). For example, if the USPTO missed the first Office Action deadline by 60 days and those 60 days also fall within the B-delay period, only 60 days — not 120 — are credited.
Applicant delay
Days during which the applicant failed to engage in “reasonable efforts to conclude prosecution” are subtracted. The most common scenario: taking more than three months to respond to an Office Action. The excess days beyond three months (or the time allowed for a non-extendable reply) are applicant-delay days, even if extensions of time were purchased. Under current USPTO practice, each day of extension of time beyond the three-month window counts as applicant delay.
The calculation
gross PTA = A-delay + B-delay + C-delay
net PTA = gross PTA − overlap days − applicant delay days
(floored at zero — PTA cannot be negative)Worked example
Filing date: Day 0 | First OA date: 15 months from filing (1 month late = ~30 A-delay days) | Issue date: 4 years from filing (1 year of B-delay = ~365 days) | Overlap: 30 days (the A-delay month falls within the B-delay period) | Applicant delay: 45 days (took 4.5 months to respond once)
gross PTA = 30 + 365 + 0 = 395 days
net PTA = 395 − 30 − 45 = 320 daysThe patent issues with a 320-day PTA, extending its term from 20 years to approximately 20 years and 320 days from filing.
Reconciling against the issued patent
The USPTO prints the PTA on the front page of the issued patent. If your calculation differs, you have a limited window — typically two months from the issue date — to petition for correction by filing a USPTO petition for PTA review. The USPTO frequently miscounts applicant delay (particularly the treatment of extension-of-time days) and overlap. A discrepancy of even a few days is worth verifying for high-value patents.
All calculations run locally in your browser and are not legal or patent advice.