Pet Vaccination Due Date Calculator

Quick answer If the last vaccination was on 31 March 2026 and your vet said the next one is due in 12 months, it is due on 31 March 2027, 164 days after 18 October 2026. This tool only adds the interval you enter; your vet sets the schedule.

How to use the pet vaccination due date calculator

Enter the date of the last vaccination.
Enter the interval your vet gave you in months.
Press Calculate.

Worked example

A last vaccination on 31 March 2026 with a 12-month interval from the vet, checked on 18 October 2026.

Date of the last vaccination: 2026-03-31
Interval your vet gave (months): 12
Check on this date (leave empty for today): 2026-10-18

Due 31 Mar 2027

Due date: 31 Mar 2027
Days to go: 164
Interval: 12 months

This only adds the interval you entered. Your vet decides which vaccines your pet needs and when.

Example values are illustrative; this result is produced by the same calculator above.

How we calculate it

due date = last date + interval in months (shortened to the last day of a shorter month); days until = due date − today

Sources: Pure arithmetic / unit conversion on user inputs (no external constant)

Understanding your result

Your vet tells you how often a vaccine is due. Enter the date of the last vaccination and the interval in months, and the calculator adds the interval to give the due date and the days remaining or overdue.

If the last vaccination was on 31 March 2026 and the next is due in 12 months, it is due on 31 March 2027, which is 164 days after 18 October 2026. If the day does not exist in the later month, the last day of that month is used.

The tool does not know which vaccines your pet needs. That depends on the pet's age, health, lifestyle and local rules, so follow your vet's schedule and call them if a date has passed.

Common mistakes

Using the date of the vet visit rather than the vaccination date.
Entering the interval in years instead of months.
Forgetting that puppies and kittens have a course with several dates.
Assuming every vaccine has the same interval.
Waiting for the calculator when a reminder from the vet is due.

Good to know

Keep your pet's vaccination record where you can find it.
Ask the vet to confirm dates for travel or boarding.
Add a reminder to your calendar a few weeks before the due date.

When to talk to your vet

The due date has passed
Your pet's schedule is unclear
Your pet is a puppy or kitten on a vaccination course

Frequently asked questions

How often does my pet need vaccinations?

That depends on the vaccine, your pet's age, lifestyle and local rules. Your vet sets the schedule; this calculator only adds the interval to the date.

What if the due date has passed?

The calculator shows that it is overdue. Contact your vet about what to do; do not guess.

Does it cover puppies and kittens?

Puppy and kitten vaccine courses follow your vet's schedule with several dates, so use the calculator once per interval your vet gives you.

Can I use it for a booster?

Yes. Enter the last date and the interval your vet gave for the booster.

What if my pet has several vaccines?

Run it once per vaccine with that vaccine's own date and interval.

Is the result a medical schedule?

No. It adds the interval you enter to a date. Your vet decides what is needed and when.

Reviewed by a licensed veterinarian

Last reviewed 18 Oct 2026 · How we review

Sources

Pure arithmetic / unit conversion on user inputs (no external constant)

Embed this calculator

Free for vets, rescues and pet blogs — no ads inside the widget.

Get embed code

This tool only adds the interval you enter to a date. Your veterinarian decides which vaccines your pet needs and when. If your pet may have eaten something harmful, contact your vet or an animal poison helpline now.