How to Read a Speed Test: Ping, Jitter, Download and Upload

The five numbers that actually matter

Run a test on InternetSpeed.co.za or any other tool and you'll see two big numbers (download and upload) and a few smaller ones (ping, and sometimes jitter and packet loss). The big numbers tell you how much data you can move. The small ones tell you how quickly and how reliably it moves. For most everyday South African use, the small numbers matter more than the big ones.

• +Download (Mbps): how fast data comes to you — streaming, browsing, downloading.
• +Upload (Mbps): how fast data leaves you — video calls, posting, cloud backups, online gaming.
• +Ping / latency (ms): the delay before data starts moving. Lower is better.
• +Jitter (ms): how much that delay wobbles. Lower and steadier is better.
• +Packet loss (%): how much data never arrives and has to be resent. You want zero.

Download and upload: speed for moving data

Download is the headline ISPs sell you on. It decides how quickly a page loads, how fast a game patch arrives, and whether Netflix or Showmax plays in HD or 4K without buffering. The good news is you need less than you think: HD streaming needs roughly 5 Mbps per screen and 4K around 25 Mbps. A busy household of four streaming, browsing and video-calling at once is comfortable on a typical entry-to-mid fibre line, and a stable LTE or 5G connection usually copes too.

Upload is the number most people ignore until it hurts. It governs how you look on a Teams or WhatsApp video call, how fast photos and videos post to social media, and how cloud backups behave. Fibre usually gives you generous upload — often symmetrical or close to it, so your upload roughly matches your download. LTE and 5G are typically lopsided: strong download but much weaker upload. That's why a fixed-wireless line can feel great for Netflix but frustrating on a long work call. If your calls freeze while your downloads fly, weak upload is usually the culprit.

• +If you only stream and browse: download is king, upload barely matters.
• +If you work from home, video-call or game: upload and ping matter as much as download.
• +A modest line that stays stable beats a fast one that drops out under load.

Ping, jitter and packet loss: the quality numbers

Ping (also called latency) is the round-trip delay in milliseconds. Think of it as reaction time, not speed. It barely affects watching a video — the buffer hides it — but it dominates anything live: online gaming, voice and video calls, and remote desktop. On a good local SA fibre line you'll often see ping in the low tens of milliseconds to a nearby Johannesburg or Cape Town server. LTE and 5G usually sit a bit higher. Test against an overseas server and ping jumps, because the data is physically travelling further — that's normal, not a fault.

Jitter is the variation in ping from moment to moment. A steady ping is far better than one bouncing around, even if the average looks fine. High jitter is what makes a call sound robotic or a game 'rubber-band' while your speed still looks healthy. Single digits (under about 10 ms) is good; jitter regularly above 30 ms will show up on calls and games.

Packet loss is the percentage of data that doesn't arrive and has to be sent again. Even small amounts wreck live activities — stuttering calls, dropped game actions, sudden buffering. You want 0%. Anything consistently above roughly 1-2% points to a real problem: a congested cell, faulty wiring, an overloaded router, or a flaky Wi-Fi link.

• +Gaming: low ping to local servers, low jitter, 0% loss.
• +Video calls: stable upload and low jitter matter more than raw Mbps.
• +Streaming: ping and jitter barely matter; consistent download speed is what counts.

Why your result is never the same twice

Two tests minutes apart can look completely different, and that doesn't mean the test is broken. In most homes the biggest factor is Wi-Fi. A wireless signal weakens through walls, fights with the neighbour's network and your microwave, and is shared across every connected device. It's completely normal to pay for a fast line and see a fraction of it over Wi-Fi in a back bedroom — the line is fine, the Wi-Fi is the bottleneck.

Server distance matters too. Testing against a server in your own city flatters your ping; testing against London or New York adds real, unavoidable delay. Congestion is the third factor: South African networks get busy in the evening peak (roughly 7-10pm) when everyone streams at once, and shared LTE/5G cells slow down when many people in your area are online. So-called 'uncapped' lines can also be throttled or shaped under a Fair Use Policy (FUP) once you've moved a lot of data. And load-shedding plays a hidden role: a tower or local node running on backup may perform differently, and your own router and ONT need power and a few minutes to fully reconnect after an outage.

How to test properly so the number means something

If you want a result you can trust — especially before phoning your ISP to complain — do a clean test. The goal is to measure the line, not your Wi-Fi or a busy household.

Done this way, a slow result points the finger clearly. If a wired test is fine but Wi-Fi is slow, fix the Wi-Fi. If even a clean wired test is far below what you pay for, the problem is the line or the network — and you've got the evidence to raise it.

• +Plug a laptop into the router with a network cable if you can — this takes Wi-Fi out of the equation.
• +Close everything else first: pause downloads, streaming, backups and other devices.
• +Run it 2-3 times and look at the pattern, not one lucky or unlucky run.
• +Test at different times — once off-peak (daytime) and once in the evening peak — to spot congestion.
• +Use a nearby (South African) test server to judge your line; use a distant one only to understand overseas latency.
• +If you must use Wi-Fi, stand near the router so a weak signal doesn't get blamed on the ISP.

What the numbers mean for real activities

Translating the metrics into daily life makes them far easier to judge. Match the activity to the number that actually limits it, and you'll know whether your connection is a genuine problem or perfectly adequate.

• +Watching Netflix/Showmax/DStv Stream in HD: ~5 Mbps download per screen; ping and jitter irrelevant.
• +4K streaming: ~25 Mbps download per screen, stable rather than spiky.
• +Zoom/Teams/WhatsApp video calls: a few Mbps up and down, low jitter — upload stability is make-or-break.
• +Competitive online gaming: download barely matters; chase low ping, single-digit jitter and 0% packet loss.
• +Working from home / cloud files: decent upload is essential, not just download.
• +Big game and software downloads: pure download speed — the one time a very fast line really shines.

Frequently asked questions

What is a good ping for South Africa?

To a local SA test server, anything in the low tens of milliseconds is good — typically lower on fibre and a bit higher on LTE/5G. Under about 50 ms is comfortable for gaming and calls. Higher ping to overseas servers is normal because the data travels much further, so judge your line against a nearby server.

Why is my speed test slower than the line I pay for?

Most often it's Wi-Fi: distance, walls and other devices all cut wireless speed, so a fast line can read a fraction of its rated speed in another room. Other causes are evening congestion, testing against a far-away server, background downloads eating bandwidth, or FUP shaping on an 'uncapped' plan. Do a wired test with nothing else running to see the line's true speed.

Does upload speed really matter, or just download?

It depends what you do. For streaming and browsing, download is almost everything. But if you work from home, make video calls, post videos or game online, upload matters just as much — it's what keeps you smooth on a call. This is the main reason fibre often feels better than LTE/5G for work: fibre's upload is usually much stronger.

What are jitter and packet loss, and why are they bad?

Jitter is how much your ping wobbles from moment to moment; packet loss is the percentage of data that never arrives and must be resent. Both ruin live activities — stuttering calls, robotic voices, rubber-banding games — even when your Mbps looks healthy. Aim for jitter in single digits (under ~10 ms) and packet loss at 0%.

How many times should I run a speed test?

Run it at least 2-3 times in a row and look at the pattern rather than trusting a single result. For a fuller picture, also test at different times of day — once during quiet daytime hours and once in the busy 7-10pm peak — so you can tell a genuinely slow line from ordinary evening congestion.