Toothpaste Calculator
Enter your tube size, how many times a day you brush, how much toothpaste you use each time, and how many people share the tube. The calculator tells you how many days the tube lasts, how many tubes you go through per year, and what that costs annually. Switch between millilitres and fluid ounces at any time.
How to use this calculator
Select your volume units (metric or imperial), then enter the capacity printed on your tube. Adjust the wastage percentage - 10% is a typical amount left stuck in the tube. Choose how much toothpaste you use per brush using the drop-down (the American Dental Association recommends one pea-sized amount, roughly 0.25 mL or a centimetre-wide dab). Enter how many times per day you brush and how many people share the tube. If you enter the price you pay per tube, the calculator also shows your annual spend and how much you would save by switching to the recommended amount.
How the duration formula works
The calculation starts with the printed tube capacity and subtracts your wastage percentage to find the usable volume. It then multiplies your amount per brush by the number of daily brushing sessions and the number of people sharing the tube to get a daily usage figure. Dividing usable volume by daily usage gives the number of days the tube lasts. Dividing 365 by that number gives tubes per year, and multiplying by price per tube gives annual cost. For example: a 100 mL tube with 10% wastage has 90 mL usable. One person brushing twice daily with one pea-sized amount uses 0.25 x 2 = 0.5 mL per day, so the tube lasts 90 / 0.5 = 180 days.
Why the recommended amount matters
Toothpaste advertisements famously show a thick ribbon covering the entire brush head - roughly four times the clinically recommended amount. Fluoride toothpaste is effective at a pea-sized dose (about 0.25 mL) because the active fluoride ions are already present in sufficient concentration. Using more toothpaste does not improve cleaning. For children under six, the recommended amount is even smaller: a smear the size of a grain of rice (about 0.1 mL) for children under three, and a pea-sized amount for those aged three to six. Using the recommended amount can roughly halve or quarter your annual spend on toothpaste.
Minimising tube wastage
Rolling the tube from the bottom as it empties, using a tube squeezer clip, or cutting the tube open to scrape out the last remnants can reduce wastage from the typical 10-15% down to 2-5%. Over a year, that can add up to an extra brushing-week or two of toothpaste. Storage also matters: keeping the cap on prevents the paste near the opening from drying out and becoming difficult to squeeze, which contributes to wastage.
Common tube sizes and expected duration
| Tube size | Usable volume | Days (1 person, 2x/day) | Tubes per year |
|---|---|---|---|
| 30 mL (1 fl oz, travel) | 27 mL | 54 days | 6.8 |
| 75 mL (2.5 fl oz, standard) | 67.5 mL | 135 days | 2.7 |
| 100 mL (3.4 fl oz, standard) | 90 mL | 180 days | 2.0 |
| 125 mL (4.2 fl oz, family) | 112.5 mL | 225 days | 1.6 |
| 150 mL (5 fl oz, family) | 135 mL | 270 days | 1.4 |
Duration estimates assume one person brushing twice daily with one pea-sized amount (0.25 mL) and 10% wastage.
Frequently asked questions
How long does a tube of toothpaste typically last?
A standard 100 mL tube, used by one person brushing twice daily with the recommended pea-sized amount (0.25 mL) and accounting for about 10% wastage, will last roughly 180 days or six months. Using more toothpaste per brush, brushing more often, or sharing the tube with family members all shorten that figure significantly. The calculator above works out your specific duration from your own inputs.
What is a "pea-sized" amount of toothpaste?
A pea-sized amount is approximately 0.25 mL, roughly the diameter of a standard garden pea. In practice, it looks like a small dab about the width of a pea sitting on top of the brush bristles, not a ribbon running the length of the brush head. The American Dental Association (ADA) recommends this amount for adults because it delivers enough fluoride for effective protection without requiring more.
Does using more toothpaste clean teeth better?
No. The mechanical action of brushing does the cleaning work, and a pea-sized amount of toothpaste provides more than enough fluoride and abrasive contact to do the job. Larger amounts create more foam, which can feel more satisfying, but they do not improve plaque removal or cavity prevention. Toothpaste manufacturers and advertisers have historically depicted larger portions to increase consumption.
How much toothpaste should children use?
The American Academy of Pediatric Dentistry recommends a rice-grain smear (about 0.1 mL) for children under three years old, and a pea-sized amount (0.25 mL) for children aged three to six. Children are more likely to swallow toothpaste rather than spit it out, so limiting the amount reduces the risk of ingesting too much fluoride.
How do I find the best value tube?
Compare cost per millilitre rather than cost per tube. Divide the price by the tube capacity. Larger tubes almost always have a lower cost per mL. If the calculator shows you need, say, 2.7 tubes per year, buying a larger format that covers more than half a year per tube will typically be cheaper overall than buying small tubes more often.
Does toothpaste expire?
Yes. Most toothpaste carries a two-year expiration date from the manufacture date, which is required by the U.S. Food and Drug Administration for fluoride toothpaste. After expiry, the fluoride concentration may fall, reducing effectiveness. Opened tubes are generally best used within 12 months. If a tube would last you more than a year based on this calculator, consider buying smaller quantities so you always use a fresh tube.