On this page
Where our numbers come fromHow we pick a number when sources disagreeHow we choose the formulasHow we handle metric and imperialHow often we checkFound a number that looks wrong?Last updated: 17 July 2026
This page explains, in plain words, where the numbers on Vriksai come from and how we keep them honest. If you ever want to know why a figure says what it says, this is the page to read.
1. Where our numbers come from
Every number on Vriksai — density, hardness, shrinkage, strength, durability — is taken from a published book or standard that anyone can check. We do not guess, and we do not copy numbers from random websites or forums.
Our main sources are:
- USDA Wood Handbook (GTR-190) — the big reference book from the US Forest Products Laboratory. We use it for density, strength and moisture behaviour.
- The Wood Database — used for Janka hardness and shrinkage figures.
- PROSEA — a plant resource reference we use for South-East Asian woods.
- EN 350 — the European standard for how well a wood resists rot.
- Finnish ThermoWood Association — for heat-treated wood.
- IS 875 and IS 1902 — Indian standards we use for wind load and log volume.
Each species page and reference page lists the source it used, right at the bottom.
2. How we pick a number when sources disagree
Sometimes two books give slightly different figures for the same wood. This is normal — a tree grown in one place is not exactly the same as the same tree grown somewhere else. When this happens, we do a few simple things:
- We prefer the number from the more trusted source (a national standard or the USDA handbook comes first).
- We use a typical or average value, not the highest or lowest one, so it is safe to plan with.
- Where a wood naturally varies a lot, we say so on the page instead of pretending there is one exact number.
3. How we choose the formulas
Every calculator uses a formula from a known, published source — a standard, a handbook, or a long-used trade rule. We do not invent our own maths. On each tool page we show the formula and name where it comes from, so you can check it yourself.
Where a formula is well known but not from a single official standard (some old log rules, for example), we say that clearly too.
4. How we handle metric and imperial
Wood is measured in different units around the world — cubic feet in India, board feet in America, cubic metres almost everywhere else. Our tools let you switch between them, and the same wood always gives the same real answer whichever unit you pick. We test this on purpose, because a unit mistake is the kind of error that looks correct but is quietly wrong.
5. How often we check
We re-check our data against the sources during site-wide reviews. The most recent full review was finished on 17 July 2026 and covered all 61 calculators and 60 species pages. When we find a mistake, we fix it on every page it affects, not just the one that was reported. Each page shows its own last-updated date so you can see how fresh it is.
6. Found a number that looks wrong?
Please tell us. If you have a better source, share it and we will check it. Real corrections are made within a few days and the page date is updated. You can reach us on our contact page.