Relay Takeover and Reaction Time Calculator

The margin between an incoming swimmer’s touch and the outgoing swimmer’s feet leaving the block, to the hundredth of a second, with the World Aquatics rule and the timing manufacturer’s published tolerance either side of it. Exactly zero is legal; negative is a relay break.

Last updated 12 Oct 2026

Takeover margin from two clock readings

Feet off − touch

Incoming swimmer touches, clock readingIn seconds from the start of the race, as the touchpad records it. Part Two Article 11.1.4 has the automatic equipment record “times to an accuracy of one hundredth (1/100) of a second”, so this is a figure to two decimal places.

Outgoing swimmer’s feet leave the block, clock readingIn seconds from the start of the race, as the block sensor records it. Swiss Timing’s own note says the system “is looking for the last registered impulse from the starting block, within a window of 4 seconds” and that the difference “is issued 2 seconds after the touch on the pad”.

0.18secondsExample

Incoming swimmer touches at 47.82 s, outgoing swimmer’s feet leave the block at 48.00 s

Formula

takeover margin Δt = (feet leave the block) − (incoming swimmer touches)
Δt below zero → the feet left before the touch
Δt at exactly zero → legal, and the tightest legal changeover there is
Δt above zero → time given away

the sign convention, and why it is this way round: World Aquatics Part Two Article 10.4.5: until an Athlete touches the wall to complete their quarter of the total race distance, “the feet of the Athlete in the same relay team who is next in order to compete must remain in contact with the starting platform”. The offence is leaving BEFORE the touch, so feet-off minus touch is negative when the rule is broken, zero when the two coincide — which is legal — and positive when margin has been given away. Transposing the two readings gives the same magnitudes with the opposite sign, and would call every legal changeover an infringement
zero is legal and is the boundary: a margin of exactly 0.00 means the feet left at the instant of the touch, not before it, so nothing in the rule is broken. The boundary is one-sided and sits exactly at zero, which is why this arithmetic has to be tested at 0.00, at −0.01 and at +0.01 rather than at one of them
the −0.03 is the equipment’s, not the rule’s: the rule has no tolerance in it. Swiss Timing’s own note on relay break detection says “a tolerance of 0.03 seconds would be given in favour of the swimmer before a relay break”, because the lag between the force leaving the block contact and the toes leaving it is “in the region of 0.024 to 0.027 of a second”. Two different kinds of number, kept apart here. The band edge on the bar sits half a hundredth below −0.03, so that a reading of exactly −0.03 lands inside the tolerance despite binary rounding
hundredths are the resolution, and that is a rule: Part Two Article 11.1.4 has the automatic equipment record “times to an accuracy of one hundredth (1/100) of a second”, and Article 11.2.3.1 says a calculation running to thousandths has “the final digit … not recorded” and “not ’rounded’ up or down”. So the margin is a two-decimal figure, truncated rather than rounded. Article 10.4.1 has each team “comprised of four (4) Athletes”, so there are three of these margins in a relay

Worked example

Incoming swimmer touches at 47.82 s, outgoing swimmer's feet leave the block at 48.00 s
48.00 − 47.82 = +0.18 s
The margin is positive, so the feet were still on the block at the touch and there is no relay break — Article 10.4.5 is satisfied
0.18 s is eighteen hundredths given away, about 0.36 m of water at a racing speed of 2 m/s
Move the feet-off to 47.82 exactly and the margin is 0.00, which is still legal: the rule forbids leaving before the touch, not at it
Move it to 47.81 and the margin is −0.01 — early, but inside the 0.03 s tolerance the timing manufacturer publishes in the swimmer's favour
Move it to 47.78 and the margin is −0.04, which is beyond that tolerance and is a relay break
At −0.03 exactly the reading is still inside the tolerance, because Swiss Timing writes the condition as “more than –0.03”

The three readings a takeover margin can be, and who says so

The rule column is World Aquatics Part Two; the equipment column is Swiss Timing’s own relay break detection note, document 801 / PHU / mra / 22.10.01 – V002. The two columns disagree between −0.01 and −0.03 and the disagreement is real rather than an artefact of this table: the rule carries no tolerance and the manufacturer does. A specialist swimming publication working through the same question concluded that −0.03 would not be disqualified while −0.04 would, and said in print that it could not find a current manufacturer specification and had assumed the 0.03 figure still stood. Neither source read here establishes that it does.
Margin Δt	What happened	Against the rule	Against the equipment
+0.18	feet still on the block at the touch, with margin to spare	satisfied — Art. 10.4.5	no break
+0.01	feet left one hundredth after the touch	satisfied — Art. 10.4.5	no break
0.00	feet left at the instant of the touch	satisfied — the rule forbids leaving BEFORE the touch	no break
−0.01	feet left one hundredth before the touch	not satisfied as written	inside the 0.03 s tolerance
−0.03	feet left three hundredths before the touch	not satisfied as written	still inside — the condition is written as “more than –0.03”
−0.04	feet left four hundredths before the touch	not satisfied — Art. 10.5 has the Referee disqualify the team	a relay break

What the equipment actually measures, in Swiss Timing’s own numbers

Every figure here is quoted from the Swiss Timing relay break detection note except the resolution, which is World Aquatics Part Two Article 11.1.4. The Swiss Timing note is dated 22 October 2001 in its own document reference, which is old; it is used because it is the only source read that explains the arithmetic in the manufacturer’s own words, and its age is part of why the currency of the 0.03 figure is left open rather than asserted.
Quantity	Published figure	Why it matters
Resolution of the margin	one hundredth of a second	Part Two Art. 11.1.4; a third decimal place is not an official number
Search window for the block impulse	4 seconds	the system takes “the last registered impulse from the starting block, within a window of 4 seconds”
Delay before the margin is issued	2 seconds	“The result (Δt) is issued 2 seconds after the touch on the pad”
Sign convention	minus for early	the margin “is marked with a minus (-) sign if the swimmer has left the starting-block before his team mate has touched the pad”
Tolerance in the swimmer’s favour	0.03 s	“If the difference (Δt) is more than –0.03, then a relay break has occurred”
Block contact to toes leaving	0.024 to 0.027 s	the measured lag that the tolerance exists to cover

Feet off minus touch, and where the rule and the equipment disagree

This page is about swimming — racing in a pool — whose competition regulations, swimming rules, facilities specifications and points tables are published by World Aquatics, the body that was FINA until it was renamed in 2023. Every figure below that belongs to an edition or a validity period is printed with it, because World Aquatics revises all of them.

A relay changeover is one of the few things in sport that is both exactly defined and measured to a hundredth of a second, and the arithmetic is a subtraction. World Aquatics Part Two Article 10.4.5 reads: until an Athlete touches the wall to complete their quarter of the total race distance, “the feet of the Athlete in the same relay team who is next in order to compete must remain in contact with the starting platform”. The offence is leaving before the touch, so the margin that matters is the time the feet left minus the time of the touch. Negative means early. Exactly zero is legal, because the rule forbids leaving before the touch rather than at it. Positive is time given away.

That sign convention is the thing to get right and it is easy to get backwards. A page computing touch minus feet-off would produce the same magnitudes with the opposite sign and would call every legal changeover an infringement, which is why this one prints the two readings back to you and is tested at 0.00, −0.01 and +0.01 rather than at a single comfortable value.

Then the complication, and it is real rather than a quibble. The rule has no tolerance. The equipment does. Swiss Timing, which builds the systems the break is detected by, publishes a note saying the margin “is marked with a minus (-) sign if the swimmer has left the starting-block before his team mate has touched the pad”, that “a tolerance of 0.03 seconds would be given in favour of the swimmer before a relay break”, and that “If the difference (Δt) is more than –0.03, then a relay break has occurred.” The reason is physical: the lag between a swimmer’s force leaving the block contact and the toes actually leaving it is “in the region of 0.024 to 0.027 of a second”, so a sensor registering just before the touch has not proved the toes went early. Between −0.01 and −0.03 the rule as written and the equipment as configured say different things, and this page prints both columns rather than reconciling them quietly.

An honest note about the article numbers. The rule text quoted on this page was read in full from a copy of World Aquatics’ Part Two: Swimming Rules, and that copy carries no edition, version or “in force as from” statement anywhere in its text. Its seventeen sections put the facilities rules at Section 15, where the Competition Regulations version June 2025 — which does carry its date, “In force as from 25 June 2025” — numbers Part Two in eighteen sections and puts them at Section 16. The current February 2026 regulations could not be fetched at all. So the wording is quoted as read and the numbers are not promised: check an article number against the edition your competition is run under. The same rules are traceable under the older SW numbering from World Aquatics’ own dated infraction card of 1 March 2023.

Two limits on the tolerance figure, stated rather than buried. The Swiss Timing note carries the document reference 801 / PHU / mra / 22.10.01 – V002, which dates it to 2001, and nothing read for this page establishes that 0.03 s is still the configured value. A specialist swimming publication hit the same wall: it attributes the figure to the timing system via an older governing-body document, states that it could not find a current manufacturer specification, and says in print that it assumed the tolerance had not changed. That is not a sound basis for a number a disqualification turns on, so the page reports the figure, names its source and date, and says its currency is unestablished. The rule, the sign and the resolution are not in doubt.

One neighbouring note. Athletics has an equivalent subject — the relay takeover zone — and this plugin’s athletics batch looked for it, could not source it to a World Athletics edition, and deliberately built nothing rather than guess. Swimming’s version is sourceable, from World Aquatics’ own rule text and the timing manufacturer’s own note, which is why it exists here and not there.

For the legs either side of these changeovers, the swimming split times calculator builds the schedule, and the swimming medley stroke order interpreter has the order a medley relay must be swum in — which is not the order an individual medley is swum in.

Frequently asked questions

Is a relay takeover of exactly 0.00 legal?

Yes. Part Two Article 10.4.5 requires the next swimmer’s feet to remain in contact with the starting platform until the incoming swimmer touches the wall, so the offence is leaving before the touch. Leaving at the instant of the touch breaks nothing, and 0.00 is the tightest legal changeover there is. Anything negative is early.

Why do negative reaction times sometimes not get disqualified?

Because the rule and the equipment are two different things. The rule has no tolerance. Swiss Timing’s note says a tolerance of 0.03 seconds is given in the swimmer’s favour, because the lag between the force leaving the block contact and the toes leaving it is about 0.024 to 0.027 of a second — so a reading just before the touch does not prove the toes went early.

How precisely is a relay takeover measured?

To one hundredth of a second. Article 11.1.4 has the automatic equipment record times to that accuracy, and Article 11.2.3.1 has a calculation running to thousandths drop its final digit rather than round. Swiss Timing adds that the system looks for the last block impulse within a four-second window and issues the margin two seconds after the touch.

How many takeovers are there in a relay?

Three. Article 10.4.1 has each team “comprised of four (4) Athletes”, each swimming a quarter of the distance under Article 10.2.1, so there are three changeovers. Article 10.4.4 also requires each exchange to start from the starting platform, with no running start from the deck.

What happens to the team if the takeover is a break?

Article 10.5 has the Referee disqualify the relay team, and the Athlete who caused the breach. On World Aquatics’ own dated infraction card for 2023-2025 the offence is listed as “Feet lost touch with the starting platform before the preceding team-mate touched the wall SW 10.13”, under the older numbering.

Related calculators

References

World Aquatics. Part Two: Swimming Rules (read 15 Oct 2026 from the copy in Special Olympics’ swimming officials resources; about 150,000 characters, ending at the heading “17.1 APPENDIX 1 – DIAGRAM OF A 50M X 25M SWIMMING POOL (8 LANES)” with no appendix body). Quoted here for Articles 9.1–9.3, 10.2.1, 10.4.1–10.4.7, 10.5, 11.1.4, 11.2.3, 11.2.3.1, 12.1, 12.2 and Section 15. IMPORTANT: THIS COPY CARRIES NO EDITION, VERSION OR “IN FORCE AS FROM” STATEMENT ANYWHERE, and its seventeen sections put the facilities rules at Section 15 where the Competition Regulations version June 2025 puts them at Section 16 and carries an extra section this copy does not have. The article text is quoted as read and the numbers are flagged as edition-dependent.
World Aquatics. Swimming Rule Quick Reference Infraction Sheet 2023-2025, “Version: 1 March 2023”, “In force as from 1 March 2023” (read 15 Oct 2026 from resources.fina.org; about 4,500 characters, the whole card). The only dated first-party source here for the relay and medley rules, in the OLD SW numbering: “Feet lost touch with the starting platform before the preceding team-mate touched the wall SW 10.13”, “Relay exchange did not commence from the starting platform SW 10.12”, “Relay team did not swim in the order listed SW 10.15”, “Incorrect individual medley stroke order SW 9.1” and “Incorrect medley relay stroke order SW 9.3”.
Swiss Timing Ltd (Chronométrage Suisse SA), Saint-Imier. Relay Break Detection, document reference “801 / PHU / mra / 22.10.01 – V002”, Nº 307.225, republished by Aquatics GB in its swimming officials documents (read 15 Oct 2026; about 3,800 characters, the whole note). The manufacturer’s own description: “All impulses from the touchpads and starting blocks are registered and memorized”, the system “is looking for the last registered impulse from the starting block, within a window of 4 seconds”, “The result (Δt) is issued 2 seconds after the touch on the pad”, and it “is marked with a minus (-) sign if the swimmer has left the starting-block before his team mate has touched the pad”. On the tolerance: “a tolerance of 0.03 seconds would be given in favour of the swimmer before a relay break” and “If the difference (Δt) is more than –0.03, then a relay break has occurred.” It reports the lag between the force leaving the block contact and the toes leaving it as “in the region of 0.024 to 0.027 of a second”, which is why the tolerance exists. The document reference dates it to 2001.
SwimSwam. “Why Was Australia’s -0.03 Relay Start Not A DQ? A Rules Deep Dive” (swimswam.com, read 15 Oct 2026). A specialist publication, not a governing body, cited because it prints the disagreement this page reports. It cites FINA FR 4.6.3 for relay take-overs being measured “to the hundredth of a second” and for the instruction that “For the differential in the relays take-off the manufacturer of the device shall be consulted”, and attributes the −0.03 s figure to the Omega timing system via an older FINA FR 4 document. Its author states they could not find a current manufacturer specification and ASSUMED the tolerance had not changed, so the currency of that figure is unestablished on both sources read here.
World Aquatics. Competition Regulations, version June 2025, “In force as from 25 June 2025” (resources.fina.org, read 15 Oct 2026; the fetch returns about 109,000 characters and stops inside Part One, Article 7.5.5.1.7, so the swimming rules are NOT in the readable text). Cited only for what did come through: that “In force as from” line and the complete Part Two contents, eighteen sections running “1 MANAGEMENT OF COMPETITIONS” … “9 MEDLEY SWIMMING”, “10 THE RACE”, “11 TIMING”, “12 WORLD RECORDS”, “13 AUTOMATIC OFFICIATING PROCEDURE”, “14 AGE GROUP RULES – SWIMMING”, “15 SWIMWEAR AND WEARABLES”, “16 SWIMMING FACILITIES AND EQUIPMENT”, “17 MEDICAL AND SAFETY SPECIFIC REQUIREMENTS FOR SWIMMING”, “18 APPENDICES”. The current February 2026 version could not be fetched at all — two attempts, both a server error.