Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Projected adult weight (lb)
32.7
Low estimate (lb)
28.8
High estimate (lb)
36.6
Percent of adult weight reached
55.1%
Pounds still to gain
14.7
Months to full size
12.0
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter current weight (lb).
- 2Enter current age (weeks).
- 3Enter expected size band.
- 4Read your projected adult weight (lb) on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Puppy growth follows a predictable curve by breed size: small breeds finish by about ten months, giant breeds keep filling out past eighteen. This projects adult weight from where the puppy is now and shows the growth still ahead.
Worked example
Using the values the calculator loads with:
Inputs
- Current weight: 18 lb
- Current age: 16 weeks
- Expected size band: Medium — 26–50 lb
Results
- Projected adult weight (lb): 32.7
- Low estimate (lb): 28.8
- High estimate (lb): 36.6
- Percent of adult weight reached: 55.1%
- Pounds still to gain: 14.7
- Months to full size: 12
What each field means
Inputs
- Current weight (lb)
- The current weight used in the calculation, measured in lb. Starts at 18 lb so you have a working example on load.
- Current age (weeks)
- The current age used in the calculation, measured in weeks. Starts at 16 weeks so you have a working example on load. Accepted range: 4–104 weeks.
- Expected size band
- Pick the option that matches your situation — the maths changes per option. Choices: Toy — under 12 lb adult, Small — 12–25 lb, Medium — 26–50 lb, Large — 51–100 lb, Giant — over 100 lb.
Results
- Projected adult weight (lb)
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Low estimate (lb)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- High estimate (lb)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Percent of adult weight reached
- Returned as a percentage. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Pounds still to gain
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Months to full size
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How accurate is this for mixed breeds?
Within roughly 10–15% once the puppy is past four months, provided you picked the right size band. Paw size is a poor predictor; current weight relative to age is much better.
Should I free-feed a growing puppy?
No — large-breed puppies grown too fast have higher rates of developmental orthopedic disease. Steady, measured growth on a large-breed puppy formula is the goal, not maximum size early.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Puppy Growth Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/puppy-growth
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/puppy-growth" target="_blank" rel="noopener">Puppy Growth Calculator — RevenueLab</a> (2026).</p>
Source: [Puppy Growth Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/puppy-growth) (2026).