Carbon Offset Calculator: Trees, Renewable Energy, and Cost

Enter a known CO2 or CO2e amount, or estimate emissions from flights, driving, electricity, natural gas, and event attendees. The calculator immediately shows trees, renewable kWh, optional cost, formulas, and editable assumptions.

Private by design: all calculations run locally in your browser. This is for planning and education, not certified credit issuance.

Last updatedJune 9, 2026

Data sourcesEPA eGRID, EPA equivalencies, EIA coefficients, NREL PVWatts, ICVCM/Offset Guide

Editable assumptionsTree rate, survival, buffer, grid intensity, yield, price

Runs locallyNo server upload or account required

Common offset examples

Presets are starting points. Replace them with your own footprint data when you have it.

Calculator inputs

I know my CO2 Estimate my CO2

CO2 target

CO2 or CO2e amount Units Offset timing

Years for total mode Offset price $/tCO2e

Electricity region and renewable assumptions

Grid intensity preset Grid intensity displaced kg/kWh REC quality discount % Technology Yield kWh/kW/yr System losses %

Tree assumptions

Avg sequestration kg/tree/yr Establishment at near zero years Ramp to full rate years Survival after planting Permanence buffer % Project duration years

Display options

Tree display kWh rounding

Results

Assumptions and sources

Factor	Default	Source and date	Uncertainty note
Tree sequestration rate	22 kg CO2/tree/year	Planning default aligned with the commonly cited 48 lb mature-tree estimate; cross-check with EPA Greenhouse Gas Equivalencies Calculator, updated November 2024.	Species, climate, age, soil, and management can move this value substantially.
Establishment years	2 years	Simplified young-tree growth assumption; editable.	Some species and sites sequester earlier or later.
Ramp years	8 years	Linear ramp model used for transparent planning.	Actual growth is not linear and can plateau or decline.
Survival rate	90%	Editable forestry planning assumption.	Use project monitoring data when available.
Permanence buffer	20%	Conservative buffer inspired by registry buffer-pool practice and quality concerns described by the Carbon Offset Guide.	Fire, drought, pests, harvest, and land-use change can reverse stored carbon.
Grid intensity	0.37 kg CO2/kWh US average	EPA eGRID 2023 data, latest update noted May 20, 2026. Country presets use public grid-intensity summaries and are editable.	Marginal and average emissions differ; local utility mix may differ from state or national averages.
Solar yield	1,200 kWh/kW/year before losses	NREL PVWatts modeling context.	Location, tilt, shading, weather, and inverter sizing change output.
Wind yield	2,500 kWh/kW/year before losses	Planning default for onshore wind capacity context.	Wind class, hub height, curtailment, and turbine design dominate output.
REC discount	0%	User-controlled quality adjustment. See ICVCM Core Carbon Principles context at ICVCM.	RECs are not automatically carbon offsets; additionality and claims rules matter.
Rounding	Trees round up; kWh to nearest 100	Display-only setting.	Underlying calculations keep unrounded values.

Formula transparency

CO2 target kg = entered tonnes x 1,000
effective tree rate = tree rate x survival x (1 - buffer)
trees, steady year = CO2 target / effective tree rate

tree total per planted tree =
  tree rate x ramp multiplier sum x survival x (1 - buffer)
trees, total mode = CO2 target / tree total per planted tree

effective grid intensity = grid kg/kWh x (1 - REC discount)
renewable kWh = CO2 target / effective grid intensity
net yield = renewable yield x (1 - system losses)
capacity kW = annual kWh / net yield
cost = tonnes CO2e x price per tonne

Worked example for 1 tonne CO2

With defaults, 1 tonne is 1,000 kg CO2. The effective steady tree rate is 22 x 0.90 x 0.80 = 15.84 kg/tree/year, so the steady-year result rounds up to 64 trees. Renewable electricity is 1,000 / 0.37 = about 2,700 kWh before display rounding.

How to use this calculator

Choose whether you already know the CO2 amount or need to estimate it from common activities.
Select a region or enter a custom electricity grid intensity, then adjust tree and renewable assumptions.
Read the summary, compare tree and renewable pathways, and use the source table to decide whether the defaults fit your case.

Offset quality guide

Offsetting works best after direct reductions: avoid, reduce, substitute, then offset residual emissions. A calculator can estimate scale, but credit quality depends on the project evidence.

Additionality

The project should happen because of offset funding, not as business as usual.

Permanence

Stored carbon should remain stored for the claimed period, with reversal risk managed.

Leakage

Protection in one place should not simply move emissions or deforestation elsewhere.

Double counting

One tonne should not be claimed by multiple buyers, inventories, or programs.

Verification standards

Look for third-party validation, transparent registries, monitoring reports, and retirement records.

Buffer pools

Forest programs may hold back credits to insure against fire, pests, disease, and other reversals.

RECs versus offsets

A REC is an electricity attribute measured per MWh. A carbon credit is usually one tonne CO2e reduced or removed.

Reduce first

Offsets should not replace practical emissions cuts in travel, energy use, procurement, or operations.

FAQs

How many trees offset 1 tonne of CO2?

With the default 22 kg CO2 per tree per year, 90% survival, and a 20% permanence buffer, 1 tonne of CO2 takes about 64 planted trees to match in a steady full-growth year. Over a 30-year planting horizon with establishment and ramp years, the same target is about 5 trees in this simplified model.

How many kWh of renewable energy offset 1 tonne of CO2?

Divide 1,000 kg CO2 by the effective grid intensity. At the default 0.37 kg CO2 per kWh, the result is about 2,700 kWh of renewable electricity. Cleaner grids need more kWh for the same claimed avoided CO2; higher-carbon grids need less.

Is planting trees a real carbon offset?

Tree planting can support carbon removal, but it is only a high-quality offset when the project is additional, measured conservatively, protected against reversal, and verified. Survival, fire risk, harvest, land rights, and long-term monitoring all matter.

What is the difference between CO2 and CO2e?

CO2 is carbon dioxide only. CO2e means carbon dioxide equivalent, a common unit that converts methane, nitrous oxide, and other greenhouse gases into the amount of CO2 with a similar warming effect over a stated time horizon.

How much does carbon offsetting cost?

The calculator multiplies tonnes of CO2e by your price per tonne. Voluntary market prices vary widely by project type, geography, certification, vintage, and quality, so the cost result is a planning estimate rather than a quote.

Are RECs the same as carbon credits?

No. A REC represents the environmental attribute of 1 MWh of renewable electricity generation. A carbon credit usually represents 1 tonne of CO2e reduced or removed. Renewable claims and carbon offset claims use different accounting rules.

Should I offset annually or once?

Use annual mode for recurring emissions such as household energy or yearly travel. Use total mode for a one-time flight, event, shipment, or project footprint that you want to balance over a chosen period.

What tree survival rate should I use?

Use a rate that matches the project evidence. A well-managed planting with monitoring may justify a higher rate; an informal planting in a harsh climate should use a lower value or a larger buffer.

Why do calculators give different answers?

Calculators differ because they choose different grid factors, flight factors, tree growth curves, survival assumptions, offset boundaries, and rounding rules. This page exposes those assumptions so you can adjust them.