What this calculator does
A pea-sized amount is about 0.25 ml, so brushing twice a day uses half a millilitre. A 100 ml tube at that rate lasts one person 200 days, or roughly six and a half months.
Most people use considerably more than a pea. The full ribbon across the brush head shown in advertising is closer to 1 ml, which cuts the same tube to 50 days. Dental guidance is consistent that a pea-sized amount is sufficient for adults and a smear the size of a grain of rice for children under three, so the advertised quantity is about four times what is needed.
The formula
Daily use is the amount per brushing multiplied by brushings per day and by the number of people sharing the tube. The tube volume divided by that daily figure gives the days it lasts. Tubes are usually labelled in millilitres or grams, and the two are close enough for this purpose since toothpaste is a little denser than water.
| Term | Meaning |
|---|---|
| Pea-sized | About 0.25 ml, the amount dental guidance recommends for adults. |
| Rice-grain smear | The recommended amount for children under three, considerably less than a pea. |
| Tube volume | Usually 75, 100 or 125 ml. Some tubes are labelled by weight in grams instead. |
The inputs explained
| Field | What to enter |
|---|---|
| Tube size (ml) | Tube size in millilitres, from the packaging. |
| Amount per brushing (pea-sized ≈0.25 ml) (ml) | Amount per brushing. A pea is about 0.25 ml; a full ribbon across the brush is closer to 1 ml. |
| Brushings per day, per person | Brushings per day per person. Twice daily is the standard recommendation. |
| People sharing the tube | People sharing the tube. |
When to use it
Working out how often to restock
Knowing whether a tube lasts a household two months or six changes how many to buy at once.
Seeing what over-squeezing costs
Using a full ribbon instead of a pea is four times the toothpaste, and the day count makes that concrete.
Packing for a trip
A travel tube of 25 ml covers one person for about fifty days at the recommended amount, which is more than most trips need.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How long does a tube last a household?
The same tube shared between different numbers of people.
| People sharing | Tube lasts | In months | Daily usage |
|---|---|---|---|
| 1 person | 200 days | 6.6 months | 0.50 ml |
| 2 people | 100 days | 3.3 months | 1.00 ml |
| 3 people | 67 days | 2.2 months | 1.50 ml |
| 4 people | 50 days | 1.6 months | 2.00 ml |
Questions
How much toothpaste should I use?
A pea-sized amount, about 0.25 ml, for adults and children over three. For children under three, a smear about the size of a grain of rice. This is consistent dental guidance, and it is roughly a quarter of the amount shown in toothpaste advertising.
How long should a tube of toothpaste last?
About 200 days for one person using a pea-sized amount twice a day from a 100 ml tube. If your tubes run out much faster than that, you are almost certainly using more than needed rather than brushing too often.
Does using more toothpaste clean better?
No. The cleaning comes from the brushing action and the fluoride, and a pea-sized amount carries enough fluoride for the job. Extra paste mostly produces more foam, which can actually make it harder to feel whether you have covered every surface.
Is toothpaste measured in millilitres or grams?
Tubes are labelled either way depending on the market. Toothpaste is somewhat denser than water, so a 100 g tube is a little under 100 ml, but the difference is small enough not to matter for estimating how long it lasts.
For another household running cost, see the shower cost calculator. For restocking a different staple, see the toilet paper calculator.