Trihybrid Cross Punnett Square Calculator
Set the genotype for each parent at three independent loci (DD, Dd, or dd) and instantly calculate the probability of every phenotype combination among the offspring — from fully dominant (A_ B_ C_) to fully recessive (aa bb cc).
Parent 1 — Locus A
Parent 2 — Locus A
Parent 1 — Locus B
Parent 2 — Locus B
Parent 1 — Locus C
Parent 2 — Locus C
Probability offspring expresses dominant phenotype for all three traits
- 1
P(A_) — Locus A
0.75Single-locus Punnett square for Dd × Dd - 2
P(B_) — Locus B
0.75Single-locus Punnett square for Dd × Dd - 3
P(C_) — Locus C
0.75Single-locus Punnett square for Dd × Dd - 4
P(A_ B_ C_) = P(A_) × P(B_) × P(C_)
0.75 × 0.75 × 0.75 × 100 = 42.19Independent assortment: multiply the three per-locus dominant probabilities.
How does this calculator work?
Select parental genotypes (DD/Dd/dd) for three independent loci. The calculator multiplies single-locus dominant/recessive probabilities to give the eight phenotype-class frequencies. The AaBbCc × AaBbCc cross gives the classic 27:9:9:9:3:3:3:1 ratio (64 total offspring). Assumes independent assortment and complete dominance.
Formula
How this is calculated
A trihybrid cross involves two parents that differ at three gene loci. Under Mendel's law of independent assortment (genes on separate chromosomes segregate independently), the probability of each multi-locus phenotype combination is simply the product of the individual per-locus probabilities.
For each locus the calculator determines the probability of the dominant phenotype using the standard single-locus Punnett square: DD × DD, DD × Dd, and Dd × DD all produce 100% dominant offspring; Dd × Dd gives 75% dominant; Dd × dd gives 50%; and dd × dd gives 0% (all recessive). Multiplying these three probabilities across the loci gives the eight phenotype-class probabilities.
The classic result for three heterozygous parents (AaBbCc × AaBbCc) is the 27:9:9:9:3:3:3:1 ratio, where 27/64 of offspring are dominant for all three traits. This calculator generalises beyond that special case to any combination of parental genotypes, including homozygous lines and test crosses. It assumes complete dominance, no epistasis, and genes on separate chromosomes (free combination).
Frequently asked questions
When both parents are AaBbCc, each locus independently produces a 3:1 dominant-to-recessive ratio. Multiplying three (3:1) ratios gives (3+1)³ = 64 total possibilities distributed as 27:9:9:9:3:3:3:1. The 27 represents offspring dominant at all three loci (3 × 3 × 3 = 27), and 1 represents offspring recessive at all three (1 × 1 × 1 = 1).
"A_" (A underscore) means the offspring has at least one dominant A allele — either AA or Aa. It covers both homozygous dominant and heterozygous genotypes. The underscore is a wildcard for the second allele, used when only the phenotype (dominant vs. recessive) matters rather than the exact genotype.
No — it assumes all three loci assort independently (Mendel's second law). Genes physically close together on the same chromosome are linked and do not assort independently; their combined probabilities differ from the simple multiplication used here. For linked genes, recombination frequencies must be considered separately.
Also known as
TG we-Calculate Editorial Team. (2026). Trihybrid Cross Punnett Square Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/trihybrid-cross-punnett-square-calculator
TG we-Calculate Editorial Team. "Trihybrid Cross Punnett Square Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/trihybrid-cross-punnett-square-calculator.
TG we-Calculate Editorial Team, "Trihybrid Cross Punnett Square Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/trihybrid-cross-punnett-square-calculator
@misc{wecalculate_trihybrid_cross_punnett_square_calculator, title = {Trihybrid Cross Punnett Square Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/trihybrid-cross-punnett-square-calculator}}, year = {2026}, note = {TG we-Calculate} }
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