Example data table
| Vigor | Canopy (cm) | Age (yrs) | Climate | Soil | Recommended (L) | Diameter (cm) | Depth (cm) |
|---|---|---|---|---|---|---|---|
| Dwarf | 60 | 2 | Mild | Balanced | 20 | 34.0 | 28.9 |
| Semi-dwarf | 90 | 3 | Warm / dry | Balanced | 40 | 40.7 | 34.6 |
| Standard | 120 | 5 | Warm / dry | Fast-draining | 90 | 53.3 | 45.3 |
| Semi-dwarf | 110 | 4 | Cool / humid | Moisture-retentive | 60 | 46.5 | 39.5 |
Formula used
This calculator estimates container volume from canopy size, then adjusts for vigor, climate, soil, age, and how long you want to wait before repotting.
- BaseLiters = 0.0035 × canopy_cm²
- RawLiters = BaseLiters × vigor × climate × soil × age × repot_horizon
- Apply a minimum volume by vigor, then round up to a practical size.
- Dimensions assume a cylinder with depth = 0.85 × diameter.
Why canopy? Citrus leaf area broadly tracks root demand. This is a planning model for home gardening, not a lab standard.
How to use this calculator
- Measure canopy diameter across the widest leaf spread.
- Select vigor based on your citrus type or rootstock.
- Pick climate and soil mix that match your conditions.
- Set the repot horizon you want to target.
- Press Calculate pot size to view results above.
- If roots circle heavily, repot sooner than suggested.
- Use fresh mix and keep the graft union above soil.
- Do not block drainage holes with gravel layers.
Canopy-to-volume mapping
This calculator starts with canopy diameter because leaf area tracks root demand in containers. A practical baseline is BaseLiters = 0.0035 × canopy_cm². For a 60 cm canopy, that is 12.6 L, then raised to the dwarf minimum. A 90 cm canopy gives 28.4 L before factors, while 120 cm gives 50.4 L, often rounding to 60–90 L.
Vigor and rootstock adjustments
Vigor changes how quickly roots occupy a pot. Dwarf types use a 0.85 factor and a 15 L minimum, semi-dwarf uses 1.00 with a 20 L minimum, and standard uses 1.15 with a 30 L minimum. If your variety grows long internodes and pushes frequent flushes, treat it as standard even if grafted.
Climate and soil drainage impacts
Warm, dry exposure increases transpiration and salt buildup risk, so the calculator applies a 1.10 climate factor to add buffer volume. Cool or humid sites use 0.95 to reduce stagnant, wet media. Fast-draining mixes apply 1.05 because they hold less water per liter, while moisture-retentive mixes use 0.95 and require stricter watering discipline.
Repot horizon and age scaling
If you want to wait longer between repots, the repot-horizon factor increases volume: about +8% per year beyond the first, capped near 1.40. Age adds up to about +3% per year, capped near 1.25, reflecting thicker trunks and higher nutrient demand. Root pruning can extend intervals by roughly six months when done with clean cuts.
Interpreting the diameter and depth output
Volume is converted to a cylindrical pot size with depth about 0.85 of diameter for stable citrus anchoring. The output helps you compare nursery pots, fabric bags, and decorative planters. Choose the next standard size when between volumes, prioritize multiple drainage holes, and keep the graft union above the mix. For tall, narrow pots, increase depth slightly, but avoid diameters over 55 cm unless staked in wind strong sites.
FAQs
How do I measure canopy diameter for accuracy?
Measure the widest leaf spread across the canopy, then measure a second line at 90 degrees. Average the two numbers. Avoid including a few stray shoots. Use centimeters for direct input.
What if my citrus is newly purchased in a small nursery pot?
Enter the current canopy size and keep the repot horizon near one year. Move up one practical size, not several. A gradual step reduces waterlogging risk while roots expand into fresh mix.
When should I repot even if the interval suggests waiting?
Repot sooner if roots circle densely, drainage slows, or the mix stays wet for days. Leaf drop after watering and persistent sour smell are warning signs. Shift to a fresh, airy mix and reset watering.
Do fabric pots change the recommended volume?
Use the same target liters, but expect faster drying and cooler root zones. Increase monitoring in warm weather, and mulch the surface. Fabric pots can reduce circling roots, sometimes extending the interval slightly.
Can I choose a deeper pot instead of a wider one?
Depth helps stability, but citrus still needs lateral root room. If selecting a taller container, keep volume the same and ensure strong drainage. Avoid extremely narrow pots that tip or stay wet at the bottom.
My current container is larger than the recommendation; is that bad?
Not always. If the tree is growing well and the mix dries within a reasonable period, keep it. If the pot stays wet too long, switch to a faster draining mix or downsize at the next root inspection.