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Timer is using the snapshot from Start; edits apply on the next Start.
Pick a starting format for boxing, kickboxing, MMA, or bag conditioning.
Use 1-30 rounds. The default is a training-length session, not a rules claim.
rounds
Enter 30-900 seconds. Three minutes is the common boxing training baseline.
sec
Use 0-300 seconds. One minute keeps corner timing familiar.
sec
Use 0-120 seconds; 10 seconds is useful for final flurries and corner prep.
sec before bell
Use 0-300 seconds. Short prep is enough for most bag and pad sessions.
sec
Audio stays local and starts only after a user presses Start.
Keep it short enough to read during a rest interval.
Leave on for hands-free training; turn off when a coach controls each phase manually.
{{ auto_advance ? 'On' : 'Off' }}
Useful for bag rounds and technical drills; disabled for very short rounds if not needed.
{{ halfway_cue ? 'On' : 'Off' }}
Set bell pattern to Silent visual cues to keep exports but mute tones.
{{ sound_cues ? 'On' : 'Off' }}
{{ sound_volume }}%
0% mutes tones while keeping visual cues and logs.
Helpful when the phone is nearby and audio is off.
{{ vibration_cues ? 'On' : 'Off' }}
The wake lock is released on pause, reset, completion, or navigation.
{{ keep_awake ? 'On' : 'Off' }}
MetricValueCorner detail Copy
{{ row.metric }} {{ row.value }} {{ row.detail }}
#PhaseRoundStartDurationCue Copy
{{ row.number }} {{ row.phase }} {{ row.round }} {{ row.start }} {{ row.duration }} {{ row.cue }}
MomentCueTiming Copy
{{ row.moment }} {{ row.cue }} {{ row.timing }}
TimeEventPhaseDetail Copy
{{ row.time }} {{ row.event }} {{ row.phase }} {{ row.detail }} 
{{ formattedJSON }}
Tags: Cardio Training, Date Time, Strength Training
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Combat-sport intervals are built around short, intense work periods and deliberate recovery. A boxing round, a kickboxing drill, an MMA simulation, and a heavy-bag conditioning session can all share the same basic shape: prepare, work, recover, repeat, then stop cleanly at the final bell.

Round timing matters because training quality depends on more than the headline round length. A three-minute work period with one minute of rest feels different from a two-minute round with thirty seconds of rest, even when the total session time looks similar. Warning cues, halfway cues, and corner reminders help athletes manage pace, finish cleanly, and use recovery periods instead of drifting through them.

Timeline showing setup time, work rounds, rest periods, warning cues, and final bell timing.

Training timers should also be kept separate from official bout rules. Rulebooks can define round length, rest intervals, ten-second warnings, and clock-stopping authority for a sanctioned event. A practice timer can mirror familiar patterns, but a coach, referee, sanctioning body, or commission controls official timing.

The useful question is whether the session plan matches the training purpose. Sparring, technical drilling, conditioning, and fight simulation need different work-to-rest demands. A good timer makes those demands visible before the first bell.

How to Use This Tool:

Start with a format close to the session you want, then adjust the exact timing and cue behavior before pressing Start.

  1. Choose a Training format. The built-in choices load pro-style boxing, amateur boxing, MMA or kickboxing, heavy-bag conditioning, or a custom plan.
  2. Set Rounds, Round length, Rest length, End warning, and Start countdown. The summary should show the total timer length, work time, rest pattern, and work density you expect.
  3. Open Advanced when cue behavior matters. Pick Bell pattern, add a short Corner note, decide whether phases auto-start, and choose halfway, sound, vibration, volume, and screen-awake settings.
  4. Fix any validation message before starting. Common blockers include a warning that is not shorter than the round, a corner note over 240 characters, a total session above four hours, or a numeric field outside its shown range.
  5. Press Start in the live timer surface. Use Pause, Next, and Reset only when the session plan or room control needs it. If you edit fields during a run, those edits apply the next time you start.
  6. Read Corner Card first, then use Round Ledger, Bell Cues, Round Load, Session Log, and JSON when you need the schedule, cue sheet, chart, event record, or structured copy of the plan.

Interpreting Results:

Total timer, Round shape, and Work density are the main planning numbers. Total timer includes setup, all work rounds, and rest before later rounds. Round shape shows the work and rest rhythm. Work density shows how much of the repeated work-rest interval is actual work, so a higher value means less recovery for the same style of session.

Round Ledger is the schedule audit. It lists each phase start and duration, so it is the best place to check that the final round does not add an extra rest period. Bell Cues is the coach-facing cue plan. It shows whether halfway cues and end warnings will appear and when they occur inside each work round.

A clean cue table does not make the plan official. The built-in formats are training defaults for practice sessions, not rules claims. For sanctioned bouts, check the current rulebook, event officials' instructions, and the person responsible for the official clock.

Output Best use Verification cue
Corner Card Quick session summary for total time, round shape, warnings, density, format, and corner note. Confirm the work and rest numbers before training starts.
Round Ledger Phase-by-phase schedule with start time, duration, round number, and cue text. Check that setup and rest phases appear only when their durations are greater than zero.
Bell Cues Round-start, halfway, end-warning, rest, and final-bell cues. Verify the end warning is shorter than the round and the halfway cue is wanted.
Round Load Stacked view of setup, work, and rest seconds by block. If the chart renderer is unavailable, use the tables and JSON for the same load data.
Session Log Runtime record of starts, pauses, skipped phases, warnings, holds, and completion. Use it to explain what actually happened during the run, not just what was planned.

Technical Details:

Round-timer math is a finite phase schedule. Optional setup time comes first. Each round contributes one work phase. Rest phases are inserted only between rounds, never after the final work phase. Cue timing is relative to the start of each work phase, while total session timing is measured from the beginning of setup or round one.

The density numbers separate two related ideas. Work density ignores setup and compares work against the repeated work-rest interval. Session density includes setup and answers how much of the whole timer is work. Those two percentages are identical only when setup is zero.

Formula Core

The core totals use seconds as the base unit. Let R be rounds, W be round length, B be between-round rest, and P be setup time.

Twork = R×W Trest = max(0,R-1)×B Ttotal = P+Twork+Trest Work density = TworkTwork+Trest×100% Session density = TworkTtotal×100%

For the default pro-style training plan, R = 6, W = 180, B = 60, and P = 15. That gives 1080 seconds of work, 300 seconds of rest, 1395 total seconds, 78.3% work density, and 77.4% session density after rounding.

Rule Core

Rule Mechanism Boundary
Setup phase Added before round one when Start countdown is greater than zero. A zero setup value removes the phase from the ledger.
Work phases One work phase is added for every round from 1 through R. Rounds must be whole numbers from 1 through 30.
Rest phases Rest is added after each work phase except the final round. A zero rest value removes rest phases, even when more rounds remain.
End warning The warning cue fires at W - warning seconds after each work phase starts. The warning must be greater than zero and shorter than the round to create a cue.
Halfway cue When enabled, the cue fires after half of the work-round duration has elapsed. It is based on elapsed seconds, so odd durations can produce a half-second crossing internally.
Manual phase hold When auto-start phases is off, the timer pauses at phase boundaries until Resume or Next is used. The session log records the hold so the runtime record differs from the planned ledger.

Preset And Validation Bounds

Format Rounds Work Rest Use as
Pro-style boxing 6 3:00 1:00 Sparring-paced training baseline.
Amateur boxing 4 2:00 1:00 Fast technical round baseline.
MMA or kickboxing 3 5:00 1:00 Fight-simulation baseline.
Heavy bag conditioning 8 2:00 0:30 Conditioning-paced bag work.
Custom User set User set User set Any plan inside the validation limits.
Field Accepted range Why it matters
Rounds 1 to 30 Controls how many work phases are created.
Round length 30 to 900 seconds Defines each work phase and the reference point for cues.
Rest length 0 to 300 seconds Applies only between rounds and changes work density.
Start countdown 0 to 300 seconds Adds setup time before round one and changes session density.
End warning 0 to 120 seconds and less than round length Creates one warning cue per work round when greater than zero.
Corner note Up to 240 characters Keeps cue text readable during rest periods and exports.
Total timer Greater than zero and no more than 14,400 seconds Prevents empty sessions and plans longer than four hours.

Accuracy and Privacy Notes:

Browser timers are useful for training, but they are not event-official timing systems. Sleep settings, background-tab throttling, battery modes, audio output, Bluetooth delay, and room noise can all affect whether a cue is seen or heard at the exact moment. Keep a coach, clock, or official timekeeper in charge when timing affects safety, scoring, or a sanctioned result.

  • Sound cues are browser-generated tones and start only after Start is pressed.
  • Vibration cues work only when the device and browser support the vibration API.
  • Keep screen awake requests a screen wake lock only when the browser allows it, and it is released on pause, reset, completion, or navigation.
  • The round plan, corner note, session log, tables, chart data, and JSON are generated in the browser after the page loads. Do not put sensitive coaching notes in a shareable URL or exported file unless you are comfortable storing them that way.
  • The chart tab depends on a chart renderer. If it cannot load, the table and JSON outputs still contain the schedule and load data.

Worked Examples:

Pro-style sparring block

Choose Pro-style boxing 3:00 / 1:00, keep Rounds at 6, leave End warning at 10 seconds, and keep Start countdown at 15 seconds. Corner Card shows a total timer of 23m 15s, 18m 00s of work, 5m 00s of rest, and about 78.3% work density. Bell Cues lists six warning events, one for each work round.

Heavy-bag conditioning with shorter recovery

Select Heavy bag conditioning 2:00 / 0:30 for eight rounds. The Round Ledger alternates work and rest until round eight, then ends at the final bell without adding another rest phase. Round Load makes the short recovery blocks visible, which helps a coach decide whether the plan fits conditioning work or needs longer rest for technical quality.

Warning value that blocks Start

If Round length is 30 seconds and End warning is also 30 seconds, the validation message says the end warning must be shorter than the round length. Lower the warning to 10 seconds or set it to 0 to turn it off. After the error clears, Bell Cues shows either the corrected warning timing or no end-warning rows.

FAQ:

Are the boxing and MMA presets official bout rules?

No. They are training defaults that use familiar round and rest patterns. Official timing depends on the current rulebook, sanctioning body, commission, division, and event instructions.

Why does the final round not include rest afterward?

The schedule adds rest only between work rounds. After the last work phase, the final bell completes the timer, so Total timer and Round Ledger do not add a recovery block that never starts another round.

Can I use it silently?

Yes. Choose Silent visual cues, turn Sound cues off, or set Sound volume to 0%. The visual timer, tables, log, and JSON still update.

What should I fix when Start is disabled?

Read the validation message above the fields. The usual fixes are bringing numeric values back inside their ranges, making the end warning shorter than the round, shortening a long corner note, or keeping the total timer at or below four hours.

Will vibration and screen-awake controls work on every phone?

No. Vibration cues and Keep screen awake depend on browser and device support. When unsupported, the timer can still run with visual and sound cues.

Does the session log replace the planned ledger?

No. Round Ledger is the planned schedule, while Session Log records runtime events such as Start, Pause, Next phase, Phase hold, warning cues, and completion.

Glossary:

Work density
The percentage of work time inside the repeated work-plus-rest interval, excluding setup.
Session density
The percentage of the whole timer that is work time, including any setup countdown in the denominator.
End warning
A cue that fires a selected number of seconds before each work round ends.
Halfway cue
A mid-round cue used for pace checks, stance switches, or output targets.
Round Ledger
The planned phase schedule, including phase number, type, round number, start time, duration, and cue text.
Wake lock
A browser permission request that asks the device to keep the screen on while the timer runs.

References: