Tree Diameter (DBH) Calculator
Turn trunk circumference into diameter at breast height in inches, centimetres and feet, plus basal area, Doyle log scale and a size class.
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Carbon Sequestration Calculator
Estimate carbon dioxide stored and absorbed by your trees from trunk diameter, species wood factor and age, with a driving-offset equivalent.
Carbon Sequestration Calculator
Chlorova · updated for 2026
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Click “Calculate” to see your results.
This is a simplified allometric estimate of above-ground biomass, not a verified carbon credit. It ignores roots, litter and soil carbon, treats a single diameter as representative of every tree you counted, and spreads stored carbon evenly across the age you enter, which real growth rings never do. Verified programmes such as i-Tree measure canopy cover, leaf area and species-specific growth alongside diameter. Any figure here is appropriate for a garden, school or community planting conversation, and inappropriate for an offset claim, a tradeable credit or a regulatory filing.
Trees trade carbon dioxide for wood, and the amount they have traded is written, roughly, in the width of their trunks. Foresters measure that with a general curve: biomass climbs steeply with diameter, about two thirds of dry wood is carbon, and carbon multiplied by 3.667 becomes the mass of gas taken from the air. Divide by the years a tree stood and you get an annual figure worth comparing with a car. Enter species, count, diameter and age to see both sides of that ledger.
Turning a Trunk Into a Carbon Figure
- Measure diameter at breast height, then enter it in inches.
- Pick the species group closest to your tree from the list.
- Count only trees that share that approximate diameter.
- Estimate age from the tree age calculator if you do not know it.
- Read CO2 stored today first, which is the standing account.
- Then read average annual uptake for the yearly comparison.
- Check the driving offset line for a shareable human figure.
- Compare a heavy oak and a light poplar at the same diameter.
- Repeat the calculation for each size class on your ground.
- Report storage and uptake separately, never as one blended number.
Diameter to Biomass to Carbon Dioxide
Biomass comes from a general allometric curve: dry above-ground weight in kilograms is 0.0503 times diameter in centimetres raised to the power 2.531, then scaled by a wood factor for species. That exponent is why diameter matters so much more than height, since a tree twice as wide carries nearly six times the wood. Carbon is conventionally taken as 48 per cent of dry mass, and multiplying carbon by 44 over 12 converts it to carbon dioxide, because the molecule carries two oxygen atoms for every carbon.
The annual figure divides the stored total by the age you enter, which is an average across a whole life rather than what the tree is pulling this year. Young, vigorous trees fix carbon faster than the lifetime average, while a mature tree keeps a huge stock and adds to it slowly. The offset conversions use the standard 4.6 metric tonnes a year attributed to an average passenger vehicle, and 0.404 kg of carbon dioxide for each mile driven.
Worked Example: Five 15-Inch Red Maples
- Select red maple, whose wood factor is the table baseline of 1.0.
- Enter five trees, 15 in at breast height, and an age of 40 years.
- Fifteen inches converts to 38.1 cm for the biomass curve.
- The curve returns roughly 505 kg of dry above-ground wood per tree.
- Carbon at 48 per cent is 242 kg, and CO2 becomes 888 kg.
- Five trees therefore hold close to 4,400 kg, or 4.4 tonnes.
- Spread over 40 years, that averages about 22 kg a year per tree.
- The whole group takes up roughly 111 kg of CO2 annually.
- Divided by 0.404 kg a mile, that offsets about 275 driving miles.
- A single 30 in white oak entered instead stores over 6 tonnes.
Wood Factors by Species Group
Factors scale a generic diameter curve for trees of the same trunk width. They track relative wood density, so dense slow oaks hold far more carbon per inch than light fast poplars.
| Species group | Wood factor | CO2 at 20 in DBH | Comment |
|---|---|---|---|
| Cottonwood | 0.75 | 1,400 kg | Fast and light |
| Sycamore | 0.85 | 1,600 kg | Quick big canopy |
| Silver maple | 0.95 | 1,750 kg | Soft, short-lived |
| Red maple | 1.00 | 1,850 kg | Honest middle |
| Sugar maple | 1.10 | 2,000 kg | Heavy, slow |
| White oak | 1.25 | 2,300 kg | Long ledger |
| Live oak | 1.40 | 2,600 kg | Densest here |
Key Terms
- Allometric equation
- A measured relationship between trunk diameter and total tree biomass.
- Wood density
- Mass of dry wood per volume, the reason heavy species store more per inch.
- Carbon fraction
- Share of dry biomass that is carbon, conventionally about 48 per cent.
- CO2 factor
- Multiplying carbon by 3.667 to add the weight of oxygen carried.
- Net sequestration
- Carbon locked into growth minus what tree and soil respire back.
- Residence time
- How long stored carbon stays out of the air before decay or fire.
What a Carbon Number Really Tells You
- A tree's carbon ledger closes when it dies or burns, so these figures describe an accumulating account rather than a permanent one.
- Popular claims that one tree absorbs a tonne each year confuse a lifetime total with an annual rate, since a fast mature hardwood is nearer a few hundred kilograms per decade.
- Species choice matters far less than diameter, because the curve is driven by trunk width, which makes the tree diameter tool the natural companion here.
- Urban trees often store less than woodland trees of equal diameter, since crowns are pruned and root volume is cut off by paving and compaction.
- Planting the next generation before the old one fails keeps the annual line from dropping to zero the season a big tree is lost.
Common Mistakes & Fixes
- Entering a diameter guessed from the bark rather than a circumference you wrapped.
- Quoting a lifetime storage total as though it had happened within one year.
- Counting the same tree twice because two household members measured it.
- Assuming a 4 in sapling already offsets much, instead of checking the annual line.
- Mixing metric and imperial inputs, since the biomass curve wants centimetres.
- Ignoring roots, litter and soil carbon, which hold a genuine further share.
- Treating a shaded lawn tree and an open-grown one as interchangeable.
When to Reach for This
Use it when a planting project needs a shareable impact figure, when a school or community garden wants an honest number rather than an impressive one, when comparing planting density against canopy retention, and when deciding whether to protect an existing large tree instead of felling it to replant. Pair it with the tree diameter tool for the input measurement, the tree age tool for growth rate, and the trees per acre planner for a new planting.
Carbon Sequestration Calculator: Frequently Asked Questions
How much CO2 does one tree absorb?
It depends on diameter, species and age. A 15 in red maple has stored roughly 900 kg of carbon dioxide across its life, which averages out near 20 to 30 kg a year. Young vigorous trees add carbon faster than that lifetime average, while old trees hold far more in total.
Why does wood density appear in the equation?
Because two trunks of identical diameter can weigh very differently. A live oak packs far more dry mass into the same cubic feet of wood than a cottonwood does, so the calculator scales the generic curve by a wood factor for your species.
Is one big tree better than many small ones?
For storage in the here and now, the big tree wins outright, since biomass rises with diameter to roughly the power 2.5. For annual uptake, a dense stand of younger fast growers can beat a single giant. The honest answer depends on whether you are counting stock or flow.
What happens to the carbon when the tree dies?
Most of it returns to the air through decay, combustion or wood use, unless the timber goes into long-lived structure. That is why these figures should be read as accumulation across the years you enter, and never as a permanent credit you can spend.
Does this include roots and soil carbon?
No. The curve covers above-ground wood, which is roughly three quarters of a tree's biomass, while soil carbon beneath a tree is both larger and far harder to estimate honestly. Adding roots would lift the numbers by about a fifth.
How do I measure the diameter this needs?
Wrap a tape around the trunk at 4.5 ft and divide by pi, which the tree diameter calculator does in inches or centimetres. On a slope start the height on the uphill side, and on a flared trunk measure above the swell.
Sources & Further Reading
- Allometric Equations for Estimating Tree Biomass — USDA Forest Service, Northern Research Station. Diameter-based biomass curves and the 48 per cent carbon fraction.
- i-Tree Eco: Structure and Purpose — USDA Forest Service. Method for converting tree measurements into carbon storage and uptake.
- Greenhouse Gas Emissions from a Passenger Vehicle — US Environmental Protection Agency. Annual vehicle emissions and per-mile carbon dioxide figures used for offsets.
Chlorova Gardening Team
Builds, checks and documents every tool we publish
Chlorova editorial review
Checked against extension-service publications
Formula verified against published references · Updated
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