The allele frequency calculator and the basal area calculator sit in the same Biology cluster on this site, and they share a shape: each takes one field measurement and turns it into a derived biological quantity under an explicit model. The allele frequency calculator reads a recessive disease frequency as q squared and estimates allele and carrier frequencies under Hardy-Weinberg assumptions. The basal area calculator reads a tree diameter at breast height and returns stem cross-sectional area, then scales it to an acre or hectare basis. Neither claims to capture everything about its subject — each is a model-based estimate with stated assumptions and clear interpretation boundaries, and the genuine choice is which biological quantity your question actually needs.
What each calculator does
The allele frequency calculator starts from a single decimal: the fraction of a population affected by a recessive condition. Treating that as q squared, it computes q = √(disease frequency), p = 1 − q, and the expected carrier frequency 2pq, plus a rounded 1-in-N carrier ratio. In the article’s worked example, a disease frequency of 0.0004 (1 in 2,500) gives q = 0.0200, p = 0.9800, and a carrier frequency of 0.0392 — about 1 carrier in 26. The result is a population-level estimate: Hardy-Weinberg equilibrium assumes a large, randomly mating population with no strong selection, mutation, migration, or drift, and real human populations often depart from that.
The basal area calculator also starts from one number: DBH in inches or centimeters. It applies the forestry constant 0.005454 × DBH² for inches-to-square-feet or 0.00007854 × DBH² for centimeters-to-square-meters, then converts the area unit to match the chosen plot basis and divides by plot area. In the article’s worked example, a 12-inch tree on a 1-acre plot gives 0.005454 × 144 = 0.7854 square feet per acre. Basal area is a density signal — stem area grows with the square of diameter — but it is not wood volume and not canopy cover.
Side-by-side comparison
| Feature | Allele Frequency Calculator | Basal Area Calculator |
|---|---|---|
| One input | Recessive disease frequency (decimal) | DBH in inches or centimeters |
| Model | Hardy-Weinberg: q², p + q = 1, 2pq | Circle area: 0.005454·DBH² or 0.00007854·DBH² |
| Outputs | q, p, carrier frequency, 1:N ratio | Stem area, then per-acre or per-hectare value |
| Worked example | 0.0004 → carrier 0.0392, 1:26 | 12 in on 1 acre → 0.7854 ft²/acre |
| Interpretation boundary | Not personal genetic counseling | Not volume, canopy, or stocking verdict |
| Field | Population genetics | Forestry inventory |
When to use which
Use the allele frequency calculator when your question is population-level genetics: how common is a disease-associated allele or its carriers in a modeled population. Check that the input truly belongs in the q-squared position — a registry prevalence, screening rate, and incidence can describe different things — and convert percents to decimals before entering them. Use the basal area calculator when your question is forestry: how much growing space does a stem occupy, and how does that compare on an acre or hectare basis. Measure DBH at the protocol’s breast height and never enter circumference as if it were diameter, because the squared term makes that error large. Both tools are most useful when the model and measurement assumptions stay explicit — treat each output as conditional on those assumptions.
Where to start
- Allele frequency calculator — Hardy-Weinberg allele and carrier frequency from recessive disease frequency.
- Basal area calculator — tree basal area from DBH, scaled to acres or hectares.
Informational note: This page is an educational comparison. The allele frequency result is a population-model estimate, not genetic counseling, diagnosis, or individual risk assessment, and the basal area result is a stand-density measure, not a wood-volume, canopy, or management verdict. Neither calculator provides clinical, medical, or silvicultural conclusions.