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Are you ready for the ISA exam?

Find out in 25 questions, or sit the full 100-question exam. Both are weighted across all 10 ISA domains and end with an honest domain-by-domain breakdown.

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Quick readiness check

25 questions · 26-minute timer

Same 10 ISA domains, same weighting, a quarter of the length. See your score and your weakest areas.

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100 questions · 105 minutes

Same pacing as the real test, with the sharpest domain-by-domain breakdown.

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Questions follow the real ISA exam's domain weights.

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Honest breakdown

See your strongest and weakest domains.

Free ISA Certified Arborist Practice Exam

This is a full-length, domain-weighted ISA Certified Arborist practice test — 100 questions in 105 minutes, drawn from a bank of more than 4,500 — plus a 25-question quick readiness check if you want a faster read. It is free, you do not need an account to take it, and you get a score and a domain-by-domain breakdown when you submit (we ask for your email to show them).

Of the people who finished this exam in the last 30 days, 23.8% scored at or above the 76% passing mark. The average score was 56.8 out of 100. That is a cold-start diagnostic rather than a pass rate — most people take it before they have finished studying — but it is a fair measure of where the average candidate stands when they begin.

What is on the ISA Certified Arborist exam

The real exam is 200 multiple-choice questions, 20 of which are unscored pretest items, over 3.5 hours. The passing score is 76% of the 180 scored questions. ISA weights the exam across ten domains, and this practice exam is drawn to match those weights — so the domain where you lose the most points here is the domain worth fixing first.

DomainShare of examFull exam (100)Quick check (25)
Safe Work Practices15%154
Pruning14%143-4
Tree Biology11%113
Tree Risk11%113
Tree Identification and Selection9%92
Installation and Establishment9%92
Diagnosis and Treatment9%92
Trees and Construction9%92
Soil Management7%72
Urban Forestry6%61-2

Weights from the ISA Certified Arborist Program Guide, revised August 2025.

Sample ISA exam questions, with explanations

Seven questions from the bank, with the reasoning written out. They are chosen to show the exam's actual style: the wrong answers are real arboricultural terms used in the wrong context, which is why recognising vocabulary is not enough to pass.

Safe Work PracticesSample 1 of 7

Which PPE is required when using a chainsaw?

  • A. Hard hat, gloves, and steel-toed boots
  • B. Ear protection, gloves, and long sleeves
  • C. Chaps, helmet, ear protection, and eye protection ✓
  • D. High-visibility vest and gloves

Why: Leg protection is the piece people leave off, and it is the one that prevents the most common serious chainsaw injury. ANSI Z133 calls for head, eye and hearing protection along with leg protection for chainsaw work on the ground. Every other option here drops at least one of those. Safe Work Practices is the single largest domain on the exam at 15%, and questions in it reward reading the option that is complete rather than the one that sounds reasonable.

PruningSample 2 of 7

Which type of pruning cut removes a branch at its point of origin?

  • A. Heading cut
  • B. Thinning cut ✓
  • C. Reduction cut
  • D. Shearing cut

Why: A thinning cut (also called a removal cut) takes a branch back to its point of origin — the parent branch or the trunk — which preserves natural form and does not trigger dense regrowth. A heading cut shortens a branch to a bud or a small lateral and produces a flush of weakly attached shoots. A reduction cut shortens a stem back to a lateral large enough to assume the terminal role. Shearing is indiscriminate heading across an outer surface. Knowing which cut produces which growth response covers a good share of the 14% Pruning domain.

Tree BiologySample 3 of 7

During periods of drought, which physiological mechanism is primarily responsible for reducing water loss from a tree's crown?

  • A. Closure of stomata via abscisic acid signaling ✓
  • B. Production of tyloses in the heartwood
  • C. Development of reaction wood in the canopy
  • D. Increased suberin production in the vascular cambium

Why: Under water stress the tree accumulates abscisic acid, guard cells lose turgor, and the stomata close — cutting transpiration within minutes. Tyloses are a real phenomenon but they block water movement inside xylem vessels in response to embolism or pathogens; they do not regulate crown water loss. Reaction wood is a mechanical response to lean or load, and suberin in the cambium is not a drought mechanism. This is a good example of the exam's style: every distractor is a genuine arboricultural term used in the wrong place.

Tree BiologySample 4 of 7

Which of the following factors is a primary environmental trigger for the reactivation of cambial growth in temperate trees during the spring?

  • A. Constant soil moisture levels
  • B. Increased temperature and photoperiod ✓
  • C. Reduced atmospheric carbon dioxide
  • D. Mechanical stress from heavy pruning

Why: Rising temperature and lengthening days are the environmental cues, working together with auxin moving down from expanding buds. Steady soil moisture is a condition for growth rather than a trigger for it, atmospheric CO2 does not swing seasonally in a way that starts cambial division, and heavy pruning provokes a wound and regrowth response — not the normal spring reactivation the question is asking about.

Soil ManagementSample 5 of 7

What is the difference in magnitude of acidity between a pH level reading of 4 vs. a pH reading of 7?

  • A. 1
  • B. 3
  • C. 100
  • D. 1000 ✓

Why: pH is a base-10 logarithmic scale, so each whole unit is a tenfold change in hydrogen ion concentration. Three units from 7 down to 4 is 10 x 10 x 10, so pH 4 is 1,000 times more acidic. The trap is option B — three units is the right count, but the question asks for magnitude, not the number of steps.

Soil ManagementSample 6 of 7

Which of the following is not one of the five major categories of soil horizons?

  • A. O
  • B. E
  • C. N ✓
  • D. B

Why: The five master horizons are O (organic), A (topsoil), E (eluviated, where material has leached out), B (subsoil, where it accumulates) and C (parent material). There is no N horizon. E is the one candidates most often wrongly assume is fake, because it is the least familiar of the real ones.

Tree Identification and SelectionSample 7 of 7

What is the correct scientific name for the oak tree genus?

  • A. Quercus ✓
  • B. Pyrus
  • C. Larix
  • D. Acer

Why: Oaks are Quercus. Pyrus is pear, Larix is larch, and Acer is maple. Tree Identification and Selection is 9% of the exam and leans heavily on genus-level Latin names, which makes learning the common genera some of the highest-yield studying available — it is pure recall with no reasoning required.

Frequently asked questions

How many questions are on the ISA Certified Arborist exam?

200 multiple-choice questions, of which 20 are unscored pretest items — so 180 count toward your score. You get 3.5 hours (210 minutes). Our free practice exam uses 100 questions in 105 minutes, which is the same pacing per question. There is also a 25-question quick readiness check with a 26-minute timer.

What score do you need to pass the ISA Certified Arborist exam?

The passing score is 76%, applied to the 180 scored questions — roughly 137 correct, meaning you can miss about 43. A figure of '48 you can miss' circulates in study groups and is wrong. ISA notes the cut score is subject to change after a job task analysis, so confirm it in the current Program Guide before your test date.

Does ISA publish a pass rate for the Certified Arborist exam?

No. ISA does not publish a pass rate or a fail rate anywhere in its Program Guide — the only percentages in that document are the ten domain weights, a member fee discount, and the 76% cut score. Any specific pass-rate figure you see quoted online, in either direction, is not sourced from the credentialing body.

Is this practice exam really free, and do I need an account?

Yes, and no signup is needed to start. Choose the 25-question quick readiness check or the full 100-question exam, answer the questions, and submit without creating an account. We ask for your email afterwards to unlock your score and the domain-by-domain breakdown.

How is the practice exam weighted?

Questions are drawn to match the published ISA domain weights: Safe Work Practices 15%, Pruning 14%, Tree Biology 11%, Tree Risk 11%, Tree Identification and Selection 9%, Installation and Establishment 9%, Diagnosis and Treatment 9%, Trees and Construction 9%, Soil Management 7%, Urban Forestry 6%. That means your practice score is comparable to a real attempt, and your weakest domain is genuinely your weakest domain. The 25-question quick check uses the same weights scaled down, with at least one question per domain, so its domain percentages are rougher than the full exam's.

How long is the quick readiness check?

25 questions with a 26-minute timer, the same time per question as the full exam (105 minutes for 100 questions). It uses the same ten domains and weights, gives you an overall score and a domain-by-domain breakdown, and is a rougher guide than the full 100-question exam because each domain has only one to four questions.

What does it cost to sit the real exam?

Enrollment is $295 for ISA members and $369 for non-members. A retake is $120 per attempt with a mandatory 30-day wait. Fees are set by ISA and change periodically — check the current Program Guide before you register.

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