How much ash will your fish leave? Estimate it in seconds
Cremated remains usually weigh about 3-5% of body weight[1]. For a fish that can mean a small urn's worth, or almost nothing. Enter a weight and see which it is.
- Instant range for any fish weight
- Plain comparison you can picture
- Honest note when there'll be very little
Ashes weight estimator
Cremated remains are mostly bone, so they typically weigh about 3–5% of body weight.
Expected ashes
1.4 oz–2.4 oz
That's about the weight of a golf ball.
Small animals, birds, reptiles and fish have light, delicate skeletons, so the amount returned can fall at or below the low end of this range.
Source: Embrace Pet Insurance - Bury or Cremate Your Dog? Costs, Pros & Cons
Next step: Get exact prices near you →
Using the estimator
How to use the estimator for a fish
Fish (e.g. koi) is already selected as the type of animal, so type in a body weight in pounds or kilograms, and the result appears as you type. You don't need to be exact. A koi weighed on a bathroom scale, or a rough guess from the length, is enough to show whether you're talking ounces or specks.
- Large koi: weigh yourself holding the wrapped, bagged fish, then weigh yourself alone, and subtract.
- Goldfish and mid-size tropicals: a kitchen scale is ideal. If the fish is frozen, weigh it in its bag and take off a few grams.
- Tiny fish: don't worry about weighing. Anything under an ounce will show a trace result, and that's the answer you need.
If you don't know the weight at all, measure the length. A 12-inch koi is roughly a pound; at 24 inches it's closer to eight. Body shape varies, so treat those as starting points.
Under the hood
How the estimate is calculated
The tool multiplies body weight by 3% for the low end and 5% for the high end. That ratio comes from pet insurer Embrace's guidance on cremated remains, which in turn reflects the bone mineral left after the soft tissue and water are gone.
Human studies back up the idea that small bodies return proportionally less. One forensic study of 100 commercial cremations found adult remains averaged 3.5%[2] of body weight, but only about 1% for the very smallest bodies. Fish skeletons are fine and light, and much of a fish's weight is water, so we'd expect fish to sit at or below the low end of the pet range.
A worked example
Worked example: a 14 lb koi and a 3 gram betta
Say your family's oldest koi weighed 14 lb. At 3% that's about 0.42 lb, and at 5% about 0.7 lb: which the estimator shows as 6.7 to 11.2 oz of ash, about the weight of a smartphone. That's enough for a small urn with some to spare for a pendant or two. A koi that size has often been in the family for many years, since koi typically live 30-40 years[3], according to Japan's koi promotion association. For comparison, our estimate for a 12 lb cat, using the same ratio, is about 6.7 oz[4], so a big koi can return as much as a house cat.
| Fish | Weight | Estimated ash | What the estimator compares it to |
|---|---|---|---|
| Jumbo koi | 20 lb | 9.6 oz to 1 lb | A can of soup |
| Mature koi | 14 lb | 6.7 to 11.2 oz | A can of soup |
| Pond comet or shubunkin | 1 lb | About 0.5 to 0.8 oz | An AA battery |
| Fancy goldfish | 4 oz | About a tenth to a fifth of an ounce | A teaspoon of sugar |
| Betta | 3 g | About 0.1 to 0.2 g | Less than a teaspoon of sugar |
The betta line is the honest one. A tenth of a gram is hard to separate from the chamber at all, and some providers will tell you they can't return anything that is definitely your fish. Our symbolic ash yield guide explains what a token return means.
Reading your result
What your result means for the choices ahead
- Several ounces or more: private cremation will give you something real to keep. Size an urn with the urn size calculator.
- Under an ounce: plan for a keepsake vial or pendant rather than an urn.
- A trace: consider a garden or planter burial, communal cremation, or a memorial that needs no ash at all. Our services page explains each one.
None of these outcomes means your fish mattered less. A tiny fish simply calls for a different kind of memorial. Our page of memorial ideas for fish includes photo prints, pond plants and tank keepsakes.
Which memorial feels right for a fish?
Tap an answer to vote and see how others answered. Anonymous.
Where it stops
What the estimator can't tell you
It can't tell you what a particular crematory will hand back, because processing, collection and how carefully the chamber is swept all vary. It can't account for a fish that lost weight through illness. And it can't say whether a token return will feel meaningful to you.
Those are questions for a phone call. Ask each provider, in plain words, what they expect to return for a fish of your fish's size. Our questions to ask a fish cremation provider help you phrase it, and you can send us your fish's details for options near you.
Price matters here too. For pets up to 30 lb, CareCredit lists US prices at communal $45-75; private $100-175[5]. Paying the private rate for a fish that will return a trace is a choice some families make gladly and others would rather avoid. The cremation cost calculator helps you weigh it.
Reader polls
What would you choose?
Vote anonymously and see how other readers answered. The results are live counts from people who visit this site, so they show real opinions, not a scientific sample.
Which fish are you thinking about right now?
Tap an answer to vote and see how others answered. Anonymous.
Which memorial feels right for a fish?
Tap an answer to vote and see how others answered. Anonymous.
Which memorial feels most like your pet?
Tap an answer to vote and see how others answered. Anonymous.
Free tools to help you plan
Ashes weight estimator
See roughly how much ash to expect back, by species and body weight.
Urn size calculator
Find the urn volume you need from your pet's weight, plus keepsake and sharing options.
Cremation cost calculator
Estimate a realistic price range for your pet's size, location and the type of cremation.
Questions people ask
Do fish leave ashes after cremation?
Larger fish do. Koi and big pond goldfish leave bone mineral that is processed into fine ash, much like any pet. Very small fish, such as bettas, guppies and tetras, may leave so little that nothing can be separated and returned. The estimator shows which side of that line your fish is on.
Why might a fish leave less ash than a cat of the same weight?
Ash is mostly bone mineral. Fish bones are fine and light, and much of a fish's weight is water, so the proportion left after cremation can be lower than for a mammal. That's why we suggest treating the fish result as an upper guide.
What does a symbolic or token return mean?
Some providers return a small vial or card with a certificate when a pet is too small to leave identifiable ash. The contents may include residue from the chamber rather than only your fish. Ask exactly what's included, and decide whether that feels meaningful before you book.
Can I weigh a frozen fish?
Yes. Weigh it in its sealed bag and subtract a few grams for the bag, or more for a towel. Freezing doesn't change the weight in any way that matters for this estimate, and it saves you handling the fish more than necessary.
Is the estimate the same for aquamation?
Roughly. Water cremation also returns bone mineral, and families often find the result whiter and finer than flame ash. The amount is broadly similar, so the estimator is still a useful guide, but ask the provider what they typically return for small animals.
Sources and our estimates
- [1] Embrace notes cremated remains typically weigh about 3-5% of the pet's original body weight. Embrace Pet Insurance - Bury or Cremate Your Dog? Costs, Pros & Cons, 2025.
- [2] In a study of 100 commercial human cremations, cremated remains averaged about 3.5% of total body weight in adults, 2.5% in children and about 1% in fetuses; this is the benchmark most pet crematories adapt for animals. Warren MW, Maples WR. The anthropometry of contemporary commercial cremation. Journal of Forensic Sciences, 1997 (PMID 9144931), 1997.
- [3] Nishikigoi (koi) typically live about 30 to 40 years depending on their environment. All Japan Nishikigoi Promotion Association - Ancient koi 'Hanako', 2024.
- [4] A 12 lb cat would be expected to return about 6.7 oz (0.42 lb) of cremated remains. Our estimate: 12 lb x 3.5% x 16 oz/lb. How we calculate.
- [5] CareCredit's pet cremation guide lists US communal cremation at $45-$75 and private at $100-$175 for pets up to 30 lb. CareCredit (Synchrony) - How Much Does Pet Cremation Cost? (Sept 2023), 2023.
Ask a provider what they'd return
Tell us what you need and where you are. We'll reply by email with clear options and prices so you can decide in your own time.