Owen Bradley Everyone has a room where the Wi-Fi mysteriously falls apart. The usual response is to buy an extender, plug it in somewhere convenient and hope. A Wi-Fi heatmap survey replaces that guesswork with a picture: a floor plan shaded by actual measured signal strength, showing exactly where coverage dies and how far your router really reaches. Free phone apps do this well enough for a home, and the whole exercise takes under an hour. This tutorial covers how to run the survey properly, how to read the dBm numbers without misinterpreting them, and how to turn the finished map into decisions about router placement, mesh nodes and channel settings.
What a Heatmap Tells You That a Speed Test Cannot
A speed test measures one point at one moment, mixing your Wi-Fi link, your broadband line and the remote server into a single number. A heatmap measures the wireless link alone, across dozens of points, and shows the shape of your coverage. That distinction matters because most home Wi-Fi complaints are coverage problems, not bandwidth problems, and no amount of upgrading your internet plan fixes a bedroom sitting at the edge of range.
The map also reveals things you would never guess. Foil-backed insulation, a brick chimney breast, a mirrored wardrobe or an underfloor heating mat can carve a dead zone out of a room that is only eight metres from the router. Seeing the boundary drawn on a plan tells you whether the fix is moving the router two metres or adding a node entirely.
What You Need Before You Start
- A smartphone or laptop with Wi-Fi. Android phones give the most detail because the platform exposes full scan results; iOS apps are more limited but still usable for single-network surveys.
- A free heatmap app. Several survey apps offer a free tier that covers a typical home, letting you import a floor plan and record measurement points.
- A floor plan. A rough sketch is fine. Draw the outline of each floor with room divisions, roughly to scale. Many apps let you draw one inside the app.
- Location permission enabled. Android requires it for Wi-Fi scanning, and surveys silently return nothing without it.
- Thirty to sixty minutes and a quiet house, since people moving around and microwaves running will skew readings.
Step-by-Step: Running the Survey
- Prepare the network. Note your SSID and which band you want to map. If your router uses one merged name for 2.4GHz and 5GHz, split them temporarily or map them separately, because their coverage shapes are completely different.
- Load or draw the floor plan. Import an image or sketch the layout in the app. Set the scale using a known measurement, such as the length of one wall, so distances are meaningful.
- Mark the router’s position on the plan. Everything you interpret afterwards depends on knowing where the signal originates.
- Plan a walking route. Cover every room in a loop, including corridors, stairwells, the garage, the loft and any outdoor area you care about. Aim for a measurement roughly every two to three metres.
- Take the first reading. Stand still, tap your location on the plan, and let the app sample. Hold the phone at chest height, in the same orientation each time, and keep your body between the phone and the router consistently or not at all. Consistency matters more than perfection.
- Walk and sample methodically. Move a few paces, stop, tap the new position, sample again. Do not sample while walking. Pause a couple of seconds at each point so the reading settles.
- Take extra readings at problem spots. Wherever streaming buffers or calls drop, place several closely spaced points. Dense sampling in trouble areas produces a far more useful map than evenly spread points everywhere.
- Include doorways and thresholds. Signal often falls off a cliff at a specific wall. Sampling on both sides of that wall shows you exactly how much it costs you.
- Repeat on every floor. Create a separate map per storey and mark where the stairs land, since vertical coverage is usually better than people expect and often changes the placement answer.
- Generate the heatmap. Let the app interpolate. Look at signal strength first, then at any secondary views the app offers such as channel overlap or noise.
- Save and export. Keep the file. After you move the router or add a node, running the same route again and comparing the two maps is the only honest way to prove the change helped.
Reading the dBm Numbers Correctly
Signal strength is reported in dBm as a negative number, and the scale trips people up because closer to zero is stronger. Minus 50 is excellent; minus 80 is nearly unusable. It is also logarithmic, so every 3 dBm change roughly halves or doubles the received power, and a 10 dBm difference is dramatic even though the numbers look close together.
- -30 to -50 dBm. Excellent. You are close to the router with a clear path. Maximum speeds available.
- -50 to -60 dBm. Very good. Reliable for video calls, 4K streaming and large downloads.
- -60 to -67 dBm. Good. This is the practical target for full coverage; -67 is the widely used threshold for reliable voice and video.
- -67 to -70 dBm. Marginal. Web browsing works, streaming stutters, calls drop occasionally.
- -70 to -80 dBm. Poor. Devices connect but throughput collapses and roaming becomes erratic.
- Below -80 dBm. Effectively a dead zone. Devices may show bars but cannot pass useful traffic.
Two extra points. First, 2.4GHz will show stronger numbers at distance than 5GHz, but that does not make it faster; it has narrower channels and far more interference. Judge each band against its own expectations. Second, a strong signal with bad performance usually points to interference or channel congestion rather than coverage, which is why checking a channel overlap view alongside the heatmap is worth the extra minute.
Turning the Map Into Placement Decisions
With a finished map, the fixes usually fall into one of four categories.
Move the Router First
If the strongest area is a corner of the house and the weak zone is diagonally opposite, you are wasting half your coverage on the garden. Moving the router towards the centre of the floor plan, up off the ground and away from metal, appliances and thick masonry, is free and often gains more than an extender would. Our guide to router placement for the best coverage in your home goes through the positioning rules in detail.
Add Mesh Nodes at the Right Distance
The classic mistake is putting a node in the dead zone. A node needs a strong backhaul link to be useful, so place it where the map shows roughly -60 to -65 dBm, partway between the router and the weak area, not inside it. The heatmap tells you exactly where that band of signal sits. For whole-home coverage across multiple floors, the best mesh Wi-Fi systems comparison covers how many nodes different house sizes typically need.
Use Wired Access Points Where You Can
If the map shows a large area that no wireless node can reach with a good backhaul, running a cable and adding an access point beats any wireless repeater. Wired backhaul removes the throughput penalty entirely. Options are covered in our roundup of the best home Wi-Fi access points.
Change Channels Before Buying Anything
If signal looks fine but performance is poor, check for neighbouring networks on the same channel. Move 2.4GHz to channel 1, 6 or 11 at 20MHz width, and pick a 5GHz channel with fewer competing networks. This costs nothing and sometimes resolves the whole complaint.
Troubleshooting the Survey Itself
The app records nothing. Almost always a missing location permission on Android, or the app being backgrounded mid-scan. Keep it in the foreground throughout.
Readings jump wildly at the same spot. You are moving, or the phone is rotating. Stand still, hold the device consistently, and let each sample settle for a couple of seconds.
The map looks smooth but wrong. Too few sample points. Interpolation invents everything between measurements, so sparse surveys produce confident-looking fiction. Add more points.
Coverage looks great but devices still drop. You may be mapping 2.4GHz while your devices sit on 5GHz. Map both bands separately, or check which band the phone was actually using during the survey.
Results differ between two surveys. Doors, people and even a car in the driveway change propagation. Survey with doors in their normal position and repeat the same route each time for comparable results.
Common Mistakes to Avoid
The most common mistake is surveying only the rooms you already suspect. Mapping the whole floor gives you the reference points that make the weak areas interpretable, and it often shows that the strong zone is somewhere nobody sits. The second is chasing bars rather than dBm; the bar indicator on a phone is a crude four-step approximation and hides the difference between a fine -62 and a marginal -69. The third is surveying with the phone in your pocket or held against your chest, since your body absorbs a surprising amount of 5GHz signal. Finally, do not treat the heatmap as a one-off. Re-run it after any change, and after buying new hardware, so you can prove the improvement instead of assuming it. If the map shows a genuinely large area to cover from a single point, a high-power model is the right answer, and our picks for the best long-range routers and the broader best routers for coverage roundup are the place to start.
Frequently Asked Questions
Do I need a paid app for a home survey?
No. Free tiers handle a typical house comfortably. Paid features mainly matter for large multi-floor commercial sites, predictive modelling and detailed reporting.
What signal strength should I aim for everywhere?
Target -67 dBm or better in every space where people actually use devices. Corridors, lofts and garages can be weaker without causing problems.
Should I map 2.4GHz or 5GHz?
Both, separately. The 5GHz map shows where your fast connections work; the 2.4GHz map shows the fallback coverage your smart home devices rely on.
Can I run a survey on iPhone?
Yes, though iOS restricts scanning of other networks, so apps generally measure only the network you are joined to. That is enough for a coverage map of your own Wi-Fi.
How often should I redo the survey?
After moving hardware, adding nodes, changing router or rearranging furniture significantly. Otherwise once a year is plenty, since neighbouring networks change over time.
Final Thoughts
A Wi-Fi heatmap survey converts a vague complaint into a map you can act on. Sketch the floor plan, mark the router, walk a methodical route sampling every couple of metres, and pay particular attention to the rooms that misbehave. Read the results in dBm rather than bars, aim for -67 dBm or better wherever devices are used, and remember that a strong signal with poor speed points at interference instead of range. Then act in order: reposition the router, change channels, place nodes where the backhaul is still strong, and only buy new hardware once the map proves you need it. Re-run the same route afterwards and you will have measured proof that your 2026 network upgrade actually worked.
