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Patent expiration date: how to calculate it

By Ipiry TeamPublished August 29, 20268 min read

Short answer

A US utility patent's expiration date is 20 years from its earliest non-provisional filing date, adjusted by any Patent Term Adjustment added for USPTO delay and any Patent Term Extension for FDA review, and shortened by any terminal disclaimer. A design patent expires 15 years from grant. But the effective date for most utility patents is earlier still, because 58.6% lapse for unpaid maintenance fees before reaching term.

A patent expiration date looks like it should be a lookup. It is a calculation, and four separate factors move it.

The number is not printed on the patent. Patents show a filing date, a grant date and a term adjustment figure. Working out when the patent actually ends is left to the reader, and most published expiry dates get at least one component wrong.

The four components

Factor	Effect on expiry	Where to find it
Statutory term	20 years from earliest non-provisional filing	Filing date on the patent
Patent Term Adjustment	Adds days	Front page, under 35 U.S.C. 154(b)
Patent Term Extension	Adds up to 5 years	Certificate of extension
Terminal disclaimer	Caps at an earlier patent's expiry	Front page or file history
Maintenance fee status	Ends the patent entirely	USPTO Patent Center

The last one is not really a component of the term — it is the reason most patents never reach it.

Step one: the statutory term

Twenty years from the earliest non-provisional filing date in the priority chain, under 35 U.S.C. 154.

Not the grant date. This is the most common error and it is off by however long prosecution took — typically two to three years, and sometimes much more.

Not the provisional filing date. A provisional gives twelve months of priority without starting the term clock. An application filed as a provisional in March 2014 and converted to a non-provisional in March 2015 has a term running from 2015.

Not the foreign priority date. An application claiming priority to an earlier foreign filing under the Paris Convention gets the benefit of that date for prior art purposes, but the twenty years run from the US non-provisional filing.

For continuations and divisionals, the term runs from the earliest non-provisional in the chain — the parent, not the continuation itself. A continuation filed in 2020 claiming priority to a 2012 parent expires in 2032, not 2040.

Patent type	Term runs from	Length
Utility	Earliest non-provisional filing	20 years
Plant	Filing	20 years
Design (filed on or after 13 May 2015)	Grant	15 years
Design (filed before 13 May 2015)	Grant	14 years

Step two: add Patent Term Adjustment

PTA compensates for USPTO examination delay and is added to the end of the term under 35 U.S.C. 154(b).

It is printed on the front page of the granted patent, in the bibliographic data near the filing date, usually as a line stating a number of days of extension. It is easy to overlook if you are not looking for it.

The amounts are not trivial. Patents that sat awaiting a first action, went through appeal, or spent years in examination can carry several hundred days — occasionally more than a thousand. On a commercially significant patent that is a year or more of additional exclusivity at the point in its life when it is usually worth most.

Add the days to the nominal date. A patent filed 12 March 2015 with 287 days of PTA expires on 24 December 2035, not 12 March 2035.

Check the figure rather than trusting it. PTA calculation errors are not rare, particularly on prosecutions involving appeals or multiple RCEs. The window to dispute is two months from grant — see patent term adjustment for how the calculation works.

Step three: apply any terminal disclaimer

A terminal disclaimer caps the term at an earlier patent's expiry date.

Filed during prosecution to overcome an obviousness-type double patenting rejection, it surrenders any term extending beyond the earlier related patent. It is permanent and irrevocable.

It overrides PTA. A continuation carrying 300 days of adjustment, subject to a terminal disclaimer against a parent that expires earlier, gets neither the adjustment nor its own nominal date — it expires when the parent does.

This is where family expiry dates diverge from expectation. A family built through continuation practice, where each member was disclaimed against the first, has every member expiring on the same day regardless of filing dates or individual adjustments.

Where to find it. Terminal disclaimers appear on the front page of the patent as a note that the term has been disclaimed, and in the file history. A patent front page marked "subject to a terminal disclaimer" needs the parent identified before its expiry can be calculated.

Step four: add Patent Term Extension, if applicable

PTE applies only to patents covering FDA-regulated products. Under 35 U.S.C. 156, one patent per approved product may recover up to five years of the time consumed by clinical trials and regulatory review, capped so that effective patent life after approval does not exceed fourteen years.

It must be applied for within sixty days of approval and is not automatic.

It stacks with PTA. A pharmaceutical patent can carry both, which is why some drug patents run well past twenty years from filing.

Only one patent per product qualifies, so a company with several patents covering the same drug chooses which to extend — normally the one with the broadest claims or the longest remaining term.

Step five: check whether it already expired

This is the step everybody skips, and it is the one that decides the answer for most patents.

58.6% of US utility patents granted in 2014 never reached their calculated expiry date. They became abandoned patents. They lapsed at a maintenance fee window years earlier.

To check:

Work out the fee deadlines from the grant date — 3.5, 7.5 and 11.5 years, each with a six-month grace period afterwards.

Look up the patent in USPTO Patent Center and check for a recorded payment at each stage that has passed.

A window and grace period both closed with no payment means the patent expired then, regardless of what the term calculation says.

A missing payment within a live grace period does not mean expiry. The patent is fully in force until the grace period ends, and treating it as dead is a serious error in a freedom-to-operate context.

A worked calculation

Patent granted 18 June 2019, filed 12 March 2015 as a non-provisional claiming priority to a provisional filed 20 March 2014. PTA of 287 days. No terminal disclaimer. Small entity.

Step	Input	Result
Earliest non-provisional filing	12 Mar 2015	Term clock starts
Provisional filing	20 Mar 2014	Ignored for term
Add 20 years		12 Mar 2035
Add PTA	287 days	24 Dec 2035
Terminal disclaimer	None	No change
PTE	Not applicable	No change
Calculated expiry		24 December 2035

Now check the fee status:

Fee	Due	Grace ends	Paid?
First	18 Dec 2022	18 Jun 2023	Yes
Second	18 Dec 2026	18 Jun 2027	Yes
Third	18 Dec 2030	18 Jun 2031	Pending

The answer today is that the patent expires 24 December 2035 if the third fee is paid, and 18 June 2031 if it is not. Those are four and a half years apart, and the difference rests on a $3,312 decision nobody has made yet.

This is why a single expiry date is often the wrong output. The useful answer is conditional.

Why database expiry dates disagree

Different tools calculate differently, and most calculate incompletely.

What a database may miss	Effect
PTA	Understates expiry by up to a year or more
Terminal disclaimer	Overstates expiry, sometimes by years
Maintenance fee lapse	Shows a live date for a dead patent
Correct priority chain	Wrong start date entirely

Maintenance fee status is the biggest gap. Most commercial databases display a calculated term date without reference to whether the patent is still in force, which means a substantial proportion of the expiry dates shown across the industry belong to patents that lapsed years earlier.

For anything that matters — a freedom-to-operate opinion, a purchase decision, an enforcement plan — calculate it from the USPTO record.

Family members expire on different dates

Continuations and divisionals share the parent's earliest filing date, so their nominal twenty-year dates align. Almost everything else about them differs.

Factor	Varies across family?
Nominal 20-year date	No — shared priority
PTA	Yes — separate prosecutions
Terminal disclaimer	Yes — depends on rejections received
Maintenance fee status	Yes — separate schedules from separate grant dates

The result is that family members expire on different dates, frequently in a different order from their grant dates, and a continuation can outlive its parent or die first depending on which fees were paid.

Check each member separately. A family expiry date is not a meaningful concept.

Why the date matters commercially

A buyer is purchasing remaining exclusivity. A patent with twelve years left is worth substantially more than one with four, and the four-year patent may cost the buyer an $8,280 maintenance fee almost immediately after acquisition.

Term adjustment is real value. A patent with 300 days of PTA has nearly a year more exclusivity than its nominal date suggests, arriving at the end of its life when the technology is usually most established.

A valuation using the nominal date is mispricing the asset — understating it where PTA applies, overstating it where a terminal disclaimer does, and getting it entirely wrong where the patent has already lapsed.

Any patent valuation that does not start from a correctly calculated expiry date is starting from the wrong place.

Calculating any patent's expiry

Find the earliest non-provisional filing date, not the provisional and not the foreign priority.
Add twenty years for a utility or plant patent, or take grant plus fifteen for a design.
Add the PTA printed on the front page.
Check for a terminal disclaimer and, if present, identify the patent it was disclaimed against and use that date instead.
Add PTE if the patent covers an FDA-regulated product.
Check maintenance fee status in Patent Center for every window that has passed.
State the answer conditionally where fees remain outstanding, because the real date depends on a decision not yet made.

Common questions

How do I calculate a patent expiration date?

Start from the earliest non-provisional filing date in the priority chain and add 20 years. Then add any Patent Term Adjustment printed on the face of the patent, add any Patent Term Extension, and apply any terminal disclaimer, which caps the term at an earlier patent's expiry. Finally check maintenance fee status, because an unpaid fee ends the patent regardless.

Does a patent expire 20 years from filing or from grant?

From filing — specifically the earliest non-provisional application the patent claims priority to. Grant date governs the maintenance fee schedule but not the term. A provisional application does not start the clock, and neither does a foreign priority application.

Where can I find a patent's expiration date?

It is not printed on the patent. You calculate it from the filing date, the PTA figure shown on the front page, and any terminal disclaimer. Some commercial databases display a calculated expiry, but those calculations frequently ignore maintenance fee status, which is the factor that ends most patents.

How does patent term adjustment change the expiration date?

It adds days to the end of the term. A patent with 300 days of PTA expires 300 days after its nominal 20-year date. The figure is printed on the front page of the patent under 35 U.S.C. 154(b) and is easy to miss, which means calculated expiry dates that ignore it are wrong by up to a year or more.

Does a terminal disclaimer change the expiration date?

Yes, it caps it. A terminal disclaimer limits the patent's term to that of an earlier related patent, so the disclaimed patent expires on the same day as the one it was disclaimed against — even if its own filing date or PTA would otherwise give it longer.

How do I check if a patent has already expired?

Compare recorded maintenance fee payments in USPTO Patent Center against the grant date. Work out the 3.5, 7.5 and 11.5-year deadlines plus six-month grace periods. If a window and its grace period both closed with no payment recorded, the patent expired then, whatever the calculated term date says.

Do all patents in a family expire on the same date?

Usually not. Continuations and divisionals share the parent's earliest filing date, so their nominal 20-year dates align — but each has its own PTA, its own maintenance fee history, and possibly its own terminal disclaimer. In practice family members expire on different dates and frequently in a different order from their grant dates.

What is the expiration date of a design patent?

15 years from the grant date for applications filed on or after 13 May 2015, and 14 years from grant for earlier ones. Design patents require no maintenance fees, so the calculated date is the actual date — there is no early lapse to account for.

Can a patent expiration date be extended?

Only by Patent Term Adjustment for USPTO delay or Patent Term Extension of up to five years for one patent per FDA-approved product. Both operate before expiry and neither is a renewal. Once a patent has expired, whether by term or by lapse, nothing extends it.

Why do patent expiration dates in databases disagree?

Because they are calculated differently. Some apply PTA and some do not. Some account for terminal disclaimers and some do not. Most do not reflect maintenance fee status at all, so they show a nominal term date for a patent that lapsed years earlier. For anything that matters, calculate it yourself from the USPTO record.

What happens on the patent expiration date?

The exclusive right ends. Anyone may make, use, sell or import the invention. Infringement claims that accrued before that date survive, subject to the six-year damages limitation, but no new infringement can occur afterwards and post-expiry royalties are unenforceable.

Does the expiration date affect what a patent is worth?

Directly. A buyer is purchasing remaining exclusivity, so a patent with twelve years left is worth substantially more than one with four — and the four-year patent may also cost the buyer an $8,280 maintenance fee almost immediately. Any valuation that uses the nominal date rather than the adjusted one is mispricing the asset.

How long does a patent last?

Twenty years from filing, but only 41.4% of US patents get there. Worked examples of what each maintenance fee decision costs, when the windows fall, and how term is adjusted.

Do patents expire?

Every patent expires, and most expire early. The two ways a patent ends, how to check whether one has, what the public domain means in practice, and the 58.6% that never reach term.

Patent term adjustment: how PTA works and how to check yours

PTA compensates for USPTO delay and is printed on the face of your patent. How the A, B and C delays are calculated, what applicant delay costs, and how to dispute a wrong figure.

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