Cross-continent latency: how much delay a call across the world really adds

You say something, there is a pause, then you both start talking at once and apologise at the same moment. Somebody blames their internet. Quite often nobody's internet is at fault: you are simply eleven thousand kilometres apart, and the gap you keep tripping over is the time it takes light to cross that distance and come back.

Delay on a long call is not a defect, it is a distance. What makes it worth understanding is that there is a hard floor — a number below which no service, no provider and no amount of money can go — and then a variable amount piled on top of it, most of which is not on the seabed but in your own flat. Knowing which part is which tells you whether to fix something or whether to simply talk differently.

These ten steps get you from "why is this awkward" to a specific number for your own route, and then to the handful of adjustments that actually help. The arithmetic is one division and you can check every figure here yourself.

Ten steps, from the physics to the conversation

Steps 01 to 04 tell you what to expect. Steps 05 onwards are the parts you can change.

1. Step 01Work out the floor for your route

   Take the distance between the two of you in kilometres and divide it by 200,000. That is your one-way delay in seconds, in the best case that will ever exist. London to New York is about 5,600 km, so 5,600 ÷ 200,000 = 0.028 seconds, or 28 ms. San Francisco to Tokyo is about 8,300 km: 41 ms. London to Sydney is about 17,000 km: 85 ms.

   Why start here — because it puts a number on the part nobody can fix. Light in glass runs at roughly two thirds of its speed in a vacuum, and that is the ceiling on how fast anything crosses an ocean. Once you know your floor, every complaint about delay becomes a question of how far above the floor you are, which is a much more answerable question.

2. Step 02Double it, then add reality

   A conversation is a round trip: your words go, their reply comes back. So double the floor. Then accept that real routes run longer than the map suggests — cables follow coastlines, skirt trenches and politics, and land where landing stations exist rather than where a ruler would put them. Every switch, router and border along the way adds its own small tax.

   A useful rule of thumb is to treat the floor as about half of what you will really see on a healthy long route, and to treat anything more than three or four times the floor as worth investigating. That is a wide band on purpose: it is the difference between "this is the planet" and "something in this path is having a bad night".

   Why it matters — this is why a transatlantic round trip typically comes in well above the 56 ms the arithmetic promises, and why a Britain-to-Australia call sits a good way above 170. It is not somebody cheating you; it is the difference between a great circle on a globe and a cable that had to go round Africa or through a strait. Expect meaningfully more than the floor and you will rarely be surprised.

3. Step 03Learn the three thresholds

   Roughly: under about 150 ms one way, a conversation feels normal and you will not detect the delay at all. Between 150 and 300 you begin to overlap each other and interrupt by accident. Past 300 you have to take turns on purpose, the way people do on a radio.

   These are figures for the whole journey from one mouth to the other ear, not just the time spent on the cable. Capturing, encoding, buffering and decoding each add a few milliseconds at both ends, which is why a route with a comfortable-looking floor can still arrive in the middle band by the time a person actually hears it.

   Why it matters — these are not made up for this page. The long-standing telecommunications guideline for interactive speech (ITU-T G.114) treats up to about 150 ms one way as fine for most applications, the range from there to roughly 400 ms as acceptable only if everyone involved knows the delay is there, and anything beyond that as unsuitable for planning purposes. Having the thresholds in your head turns "this feels off" into "we are probably somewhere past 200, so I should leave a beat".

4. Step 04Measure your own baseline instead of guessing

   Before blaming any particular call, find out what your connection does on a good day. Any ordinary network tool that reports a round-trip time to a distant server will do; run it to something on your own continent and then to something far away, and note both.

   Do it twice: once wired or sitting next to the router, and once from wherever you normally sit. The gap between those two readings is the part of your delay that lives inside your own home, and it is the only part any of this gives you direct control over. Write both numbers down; they are the reference you will compare every future bad call against.

   Why it matters — without a baseline, every bad call looks like evidence of a bad service. With one, you can tell in ten seconds whether tonight is unusual. It also exposes the case where your own connection is adding a large amount before your traffic has gone anywhere at all, which happens more often than people expect.

5. Step 05Take out the hops you actually own

   You cannot shorten the Atlantic. You can remove a congested wireless link, a VPN that is routing you through a country you have never visited, and a mobile connection that is re-negotiating with a tower every few minutes. Try a cable, or at least a better position relative to the router, and turn the VPN off for one call as an experiment.

   Why it matters — the last few metres regularly contribute more delay than an entire ocean crossing, and unlike the ocean they are yours to fix. A VPN in particular can quietly double your distance by sending everything via another continent before it starts heading towards the person you are talking to.

6. Step 06Change how you take turns

   On a long-haul call, leave a clear beat after they finish before you start. Ask fewer quickfire questions and make slightly longer statements. Avoid the reflexive "mm" and "yeah" that you would normally drop into gaps — on a delayed line they land in the middle of their next sentence.

   Why it matters — most of what makes a delayed conversation unpleasant is not the waiting, it is the collisions. Two people politely trying not to interrupt each other, both starting again at the same instant, four times in a row. One deliberate beat removes almost all of it, and after a couple of minutes you stop noticing you are doing it.

7. Step 07Stop reading the delay as a personality

   A pause before every answer is not hesitation, reluctance or boredom. Someone talking over you is not being rude. A late laugh at your joke is not a polite laugh. Assume the wire is responsible before you assume the person is.

   Why it matters — this is the part that costs people conversations. When you are meeting somebody for the first time and have thirty seconds of impression to work with, half a second of transmission delay reads as coldness if you do not know it is there. Knowing it is there means you stop scoring a stranger on the behaviour of the seabed.

8. Step 08Watch the wobble, not just the size

   Notice whether the delay is steady or jumping about. A consistent 250 ms is a call you can have all evening. A delay that swings between 60 and 400 is the one that produces stuttering audio and pictures that lurch.

   Why it matters — variation is harder to handle than distance. Everything receiving live audio holds a small buffer to smooth out packets that arrive out of step, and that buffer has to grow to cover the worst wobble it has seen, which adds delay of its own. A steady long route is genuinely easier to talk over than a short unstable one, which is why a call to the other hemisphere can feel better than a call across town on bad wireless.

9. Step 09Take the long-haul ones as voice calls when the picture is not the point

   If calls across the world keep struggling, start the next one in voice-only mode rather than hunting for a control once you are already in it. The camera control you get during a call draws a cover over the picture at both ends; it does not stop your video being sent, so it will not hand the conversation any more room. Choosing voice before you match does.

   Why it matters — the voice needs a tiny fraction of what a moving image needs, so a call that was never carrying video has far more room for everything else and usually holds steady where a video call wobbles. It also separates two problems: if a voice call over the same long route is clean, the route was congested rather than long. Distance alone does not stutter — see whose side a freeze is really on for the rest of that diagnosis.

10. Step 10Choose which part of the world you talk into

    You cannot beat physics, but you can decide which physics you get. Continents nearer to you have a lower floor, and the hour you go online decides which continents are awake — a question of clocks, not cables.

    Why it matters — a call across one ocean on a wired connection is comfortable. A call across two oceans on a busy wireless link, over a VPN, is not, and the difference is mostly choices rather than luck. If your own free hours are unusual, the arithmetic for picking a good window is in finding people awake when you are.

Where people get stuck

"I pay for gigabit, so latency cannot be my problem."

Bandwidth and latency are unrelated quantities. Bandwidth is how wide the road is; latency is how long the journey takes. A very wide road across an ocean does not shorten the ocean, and a connection can deliver enormous throughput while still taking a leisurely route to get anywhere. This is one of the most common misunderstandings on the subject.

"My speed test says 12 ms."

It says 12 ms to a server that is probably in your own city, chosen precisely because it is close. That number tells you about your access line, not about the path to somebody in another hemisphere. Run the same measurement against something genuinely far away and the picture changes completely.

"Surely 5G fixes this."

Newer mobile networks cut the delay between your handset and the mast, which is a real improvement worth having. It is also a small share of the total on a long-haul call, and it does nothing whatsoever to the several thousand kilometres in the middle. Faster radio, same ocean.

"I am on satellite internet."

Then geometry matters more than geography. A traditional geostationary satellite sits about 36,000 km up, so the signal climbs and descends before it goes anywhere useful — roughly a quarter of a second each way, before the ocean is even involved. The newer low-orbit constellations fly vastly lower and add far less. If you are on the geostationary kind, the turn-taking advice in step 06 is not optional.

"It was fine yesterday and terrible tonight."

Routes are not fixed, and neither is congestion. The path your traffic takes can change between calls, and a segment that was quiet at lunchtime can be busy at nine in the evening local time at the far end. The floor from step 01 never moves; everything above it does.

"Why does it not go straight from me to them?"

It generally does not, and that is usually to your benefit. On services like this one, your traffic joins an operator's network close to you and leaves it close to them, which is often faster and far more predictable than whatever route the public internet would improvise between two home connections. The distance is the same; the quality of the road is not.

"Can I just tell how far away someone is from the delay?"

Roughly, and it is a good party trick, but do not lean on it. A very quick, tight conversation almost certainly means you are on the same continent. A long, steady delay suggests real distance. A long, wildly variable one tells you nothing about geography at all, because it is far more likely to be describing somebody's wireless connection than their location. Ask them where they are — it is a better opener than a guess anyway.

"They sound fine but they say I am delayed."

Entirely possible. The two directions can take different paths and often do, so delay is not necessarily symmetrical. Add to that the fact that sending is the harder direction on most home connections, and one-sided delay is unremarkable. If it is sound quality rather than timing that they are describing, that is a different fix altogether: position beats price on microphones.

What the numbers are actually for

Not for winning arguments about who has the worse internet. They are for knowing when to stop trying to fix something. If you are talking to somebody on the far side of the planet and there is a third of a second between you, that is the world working correctly, and no setting exists that will improve it. What you can do is leave a beat, keep your own hops short and stop mistaking transmission delay for a personality trait.

It is worth keeping the scale in view. You are having a live conversation with a person seventeen thousand kilometres away, through glass strands lying on the floor of an ocean, and the entire complaint is that it arrives a fifth of a second late. Talking to somebody on another continent is the whole point of meeting people at random on video — the delay is the receipt.