The five-step method for every EKG strip
Before you name a rhythm, answer these five questions in the same order. Write the answers down while you are learning. After a few weeks you will do it in your head in under a minute.
- Rate. Is it slow (under 60), normal (60 to 100) or fast (over 100)?
- Regularity. Are the R to R intervals the same? Regular, regularly irregular, or irregularly irregular?
- P waves. Is there one upright P wave in front of every QRS complex? Are there extra P waves, no P waves, or sawtooth waves?
- PR interval. Is it 0.12 to 0.20 seconds (3 to 5 small boxes)? Is it the same every beat, getting longer, or unrelated to the QRS?
- QRS width. Narrow (under 0.12 seconds, fewer than 3 small boxes) usually means the beat started above the ventricles. Wide means ventricular origin or a conduction problem.
Paper basics at standard speed (25 mm/s): one small box = 0.04 seconds, one large box = 0.20 seconds, five large boxes = 1 second, and 30 large boxes = a 6-second strip.
How to work out the heart rate
Regular rhythm: the 300 and 1500 rules
Count the large boxes between two consecutive R waves and divide 300 by that number. Three large boxes gives 100 beats per minute, four gives 75, five gives 60. For more precision, count small boxes instead and divide 1500 by that number.
Irregular rhythm: the 6-second method
The 300 rule gives nonsense on an irregular rhythm like atrial fibrillation. Count the QRS complexes in a 6-second strip and multiply by 10. Ten complexes in six seconds is roughly 100 per minute.
How to use calipers on practice strips
Calipers turn a guess into a measurement. They are the single most useful habit you can build early, and they are exactly what examiners expect on paper strips.
- Check regularity: set the calipers to one R to R interval, then walk them across the strip. If each R wave lands under a tip, the rhythm is regular.
- Measure the PR interval: from the start of the P wave to the start of the QRS. Compare it beat to beat. A PR that grows until a beat drops is the signature of Mobitz I.
- March out the P waves: set the calipers to one P to P interval and walk them across. If the P waves keep a steady rhythm of their own and ignore the QRS complexes, suspect complete heart block.
ECG Quiz: EKG Rhythms & ABG
ECG Quiz has built-in calipers: drag across the strip to measure an R to R or PR interval, exactly as you would on paper, then check your answer.
Rules for 15 EKG rhythms
These are the typical textbook criteria most courses teach. Learn them in four groups rather than as one long list.
| Rhythm | Rate | Regularity | P waves and PR | QRS |
|---|---|---|---|---|
| Normal sinus rhythm | 60–100 | Regular | Upright P before every QRS, PR 0.12–0.20 s | Narrow |
| Sinus bradycardia | Under 60 | Regular | Normal P before every QRS, normal PR | Narrow |
| Sinus tachycardia | Over 100 | Regular | Normal P before every QRS (may merge into the T wave when fast) | Narrow |
| Atrial fibrillation | Variable | Irregularly irregular | No true P waves, wavy baseline, no PR | Narrow |
| Atrial flutter | Atrial about 300, ventricular often 150 (2:1) | Usually regular | Sawtooth flutter waves, PR not measurable | Narrow |
| Supraventricular tachycardia | 150–250 | Regular | P waves usually hidden | Narrow |
| Junctional rhythm | 40–60 | Regular | P absent, inverted, or after the QRS; short PR if seen | Narrow |
| Premature ventricular contraction | That of the underlying rhythm | Irregular where the early beat falls | No P before the early beat | Wide and bizarre, T wave opposite the QRS |
| Ventricular tachycardia | 100–250 | Usually regular | P waves not seen or unrelated | Wide |
| Ventricular fibrillation | Not measurable | Chaotic | None | No identifiable QRS |
| Asystole | None | None | None (occasionally lone P waves) | None; confirm leads and gain |
| First-degree AV block | Underlying rate | Regular | P before every QRS, PR over 0.20 s and constant | Usually narrow |
| Second-degree AV block, Mobitz I (Wenckebach) | Atrial normal, ventricular slower | Irregular, grouped beats | PR gets longer each beat until a QRS is dropped | Usually narrow |
| Second-degree AV block, Mobitz II | Atrial normal, ventricular slower | Irregular where beats drop | PR constant, then a P wave suddenly not conducted | Often wide |
| Complete (third-degree) heart block | Atrial faster than ventricular | Both regular, but independent | P waves march through; PR varies with no pattern | Narrow (40–60) or wide (20–40) |
The look-alikes that cost students marks
- Atrial fibrillation vs atrial flutter with variable block. Both can look irregular. Flutter has organised sawtooth waves; fibrillation has a messy baseline with no repeating shape.
- Mobitz I vs Mobitz II. Measure the PR interval of the beats before the dropped QRS. Growing means Mobitz I. Unchanged means Mobitz II.
- Sinus tachycardia vs SVT. Sinus tachycardia usually has visible P waves and a rate under about 150. SVT is usually faster with no visible P waves.
- Junctional rhythm vs sinus bradycardia. Look for the P wave. Upright and before every QRS with a normal PR is sinus. Missing, inverted or after the QRS points to junctional.
A 14-day practice plan with EKG practice strips
- Days 1–2: heart rate only. Do 30 strips a day and just calculate the rate.
- Days 3–4: the three sinus rhythms. Every strip goes through all five steps.
- Days 5–7: atrial rhythms: atrial fibrillation, atrial flutter, SVT, junctional.
- Days 8–10: ventricular rhythms: PVCs, VT, VF, asystole.
- Days 11–13: the four AV blocks, using calipers on every strip.
- Day 14: a timed mixed test. Note which rhythms you missed and go back to that group.
The rule that matters most: practise on strips you have not seen. If you reuse the same ten worksheet pictures, you end up recognising the picture instead of the rhythm.
ECG Quiz: EKG Rhythms & ABG
ECG Quiz follows the same order: Learn section, Rate Drill, then Rhythm Quiz, Speed Round, 20-question Mock Exam and a Weak Areas mode that brings back the rhythms you keep missing.
Frequently asked questions
How many EKG rhythms do I need to know as a nursing student?
Most nursing, telemetry and ACLS courses expect you to recognise around 15 basic rhythms: the three sinus rhythms, atrial fibrillation, atrial flutter, SVT, junctional rhythm, PVCs, ventricular tachycardia, ventricular fibrillation, asystole and the four AV blocks. Check your own course outline, because some add paced rhythms or torsades.
What is the fastest way to learn EKG rhythms?
Use one fixed method on every strip (rate, regularity, P waves, PR interval, QRS width), learn the rhythms in groups (sinus, atrial, ventricular, blocks) and practise on new strips every day rather than rereading the same textbook pictures. Short daily sessions work better than one long session.
How do you use calipers on an EKG strip?
Place one tip on the peak of an R wave and the other on the next R wave. Without changing the width, walk the calipers along the strip. If every R wave lands under a tip, the rhythm is regular. Do the same with P waves to check whether they march out on their own, which is the key clue in complete heart block.
How do I calculate heart rate on a strip?
For a regular rhythm divide 300 by the number of large boxes between two R waves, or 1500 by the number of small boxes. For an irregular rhythm count the QRS complexes in a 6-second strip and multiply by 10.
Where can I get EKG practice strips with answers for free?
ECG Quiz is free to download on Android. It generates a new strip every time, so you cannot memorise the picture, and it explains rate, rhythm, P waves, PR interval and QRS width for each answer.
ECG Quiz: EKG Rhythms & ABG
Unlimited EKG practice strips generated on your phone, built-in calipers, a heart-rate drill, an ABG quiz and an explanation for every answer. Works offline, no login.
More guides from AK Apps Studio
This page is for education and exam revision only. The rhythm rules on this page describe typical textbook findings; real tracings vary and must be interpreted by a qualified clinician in the context of the patient. ECG Quiz is a study tool, not a medical device.