Chromosome Number Calculator
Diploid and Haploid Chromosome Counts, by Species
Chromosome number is one of the most basic facts about a species' genome, yet it isn't predictable from body size, complexity, or evolutionary relatedness — a fruit fly gets by on 8 chromosomes while a dog carries 78. This reference tool looks up the standard diploid (2n) count for common species and derives the haploid (n) count found in their gametes.
The Formula
Haploid Number (n) = Diploid Number (2n) ÷ 2
Diploid organisms carry two full sets of chromosomes — one inherited from each parent. Gametes (sperm and egg cells) carry only one set, the haploid number, so that fertilization restores the full diploid count in the offspring.
Reference Table
| Species | Diploid (2n) | Haploid (n) |
|---|---|---|
| Fruit Fly | 8 | 4 |
| Cat | 38 | 19 |
| Pig | 38 | 19 |
| Mouse | 40 | 20 |
| Rat | 42 | 21 |
| Rabbit | 44 | 22 |
| Human | 46 | 23 |
| Chimpanzee | 48 | 24 |
| Cow | 60 | 30 |
| Horse | 64 | 32 |
| Dog | 78 | 39 |
| Chicken | 78 | 39 |
Why Chromosome Number Isn't a Complexity Ranking
- No relationship to organism complexity — the dog and chicken share the same diploid count (78) despite being very distantly related, while humans have fewer chromosomes than either.
- A common comparative genetics reference point — chromosome number is one of the first facts checked when comparing genome organization across species or setting up a karyotyping study.
- Relevant to interspecies hybrid biology — mismatched chromosome counts between related species are a major reason many interspecies hybrids (like mules, from horses and donkeys) are sterile.
How to Use This Calculator
- Select a species from the list.
- Select Calculate to see its standard diploid (2n) and haploid (n) chromosome counts.
Related Calculations
Working with DNA at the molecular rather than chromosomal level? See the DNA Molecular Weight Calculator or model a specific cross with the Punnett Square Calculator.