What MAI Should You Use?
Mean annual increment is cubic metres per hectare per year, averaged over the rotation. It is the number that captures site quality, species and management in one figure.
| Situation | Indicative MAI (m³/ha/yr) |
|---|---|
| Poor site, unmanaged, wrong species | Under 5 |
| Average smallholder plantation, some weeding | 8 – 15 |
| Well-managed eucalyptus on a good site | 20 – 30 |
| Exceptional site, matched clone, full management | 30 – 40+ |
| Pine on a reasonable site | 10 – 20 |
| Teak | Lower — long rotation, high value per m³ |
These are broad bands, not predictions for your stand. MAI varies with rainfall, soil depth, species, genetics, spacing and above all whether the block was weeded in year one. If your country's forestry service publishes yield tables for your species and site class, use those instead.
Setting the Thinning and Defect Loss
- Unthinned eucalyptus pole crop: 0–10%. Most stems are saleable in some grade.
- Thinned pine or teak: 30–50%. You are deliberately removing stems to concentrate growth — but that removed volume is not lost, it is sold or used earlier as thinnings.
- Fire, pest or storm damage: add it explicitly rather than pretending it away.
- Poor form from tight spacing: if the stand was planted too dense and never weeded, a large share may only reach firewood grade. Model that honestly.
What This Cannot Tell You
An estimate is not an inventory
- This gives you total volume. It cannot give you volume by grade, and grade is what sets price.
- It assumes an average growth rate applied evenly. Real stands are patchy — better on the mid-slope, worse on the ridge.
- Buyers price unmeasured timber defensively. An estimate does not change that; a measured inventory with a stated methodology does.
- Use this for planning and feasibility. Use a measured inventory for selling, valuing or financing.
Turn the volume into money with the investment calculator, or work out stocking with the spacing calculator.
Frequently Asked Questions
What is mean annual increment (MAI)?
The average volume a stand adds per hectare per year across the whole rotation, measured in cubic metres per hectare per year.
It rolls site quality, species, genetics and management into one number. Multiply it by rotation age to get standing volume per hectare.
What is a good MAI for eucalyptus?
A well-managed eucalyptus plantation on a good site commonly runs 20–30 m³/ha/yr, and exceptional sites with matched clonal material can exceed 30.
Average smallholder plantations with partial weeding sit nearer 8–15, and poor sites with the wrong species fall below 5. The single biggest controllable factor is year-one weeding.
How do I work out how much timber my plantation will produce?
Multiply MAI by rotation age to get cubic metres per hectare, then by your planted area, then deduct thinning and defect losses.
For a real sale you need a measured inventory instead — this gives total volume, but price is set by volume by grade.
Why does the calculator ask for survival separately?
Because MAI is a per-hectare figure that already reflects stand-level growth, while survival tells you how that volume is distributed across stems.
Survival matters for the per-tree figure, which is what you need when a buyer quotes per pole rather than per cubic metre.
Is this accurate enough to sell on?
No, and you should not. It is a planning and feasibility estimate built on an average growth rate applied evenly to a stand that is really patchy.
Selling, valuing or financing needs a measured inventory with systematic plots and a stated methodology a buyer can verify.