The answer in two lines
Choose the conduit size so that the total area of the wires is no more than 40% of the conduit's inner area when it carries 3 or more wires (per NEC Chapter 9 Table 1). In practice: a 16 mm conduit is comfortable for one lighting or socket circuit (3 wires of 1.5 or 2.5 mm²), and 19 or 23 mm when the wire is 4 or 6 mm² (such as an AC line) or when you run more than one circuit. Anti-fire means its material does not propagate flame (non-flame propagating per IEC 61386), which is the safer choice inside false ceilings and enclosed spaces. The electrician confirms the final size.
"Which conduit size are we using?" is a question asked on the first day of electrical rough-in in any apartment. A conduit that is too narrow makes pulling the wire hard and can damage its insulation, and a conduit packed with wires runs hotter. In this guide from Tawredaat (توريدات), an electrical and finishing materials store in Cairo and Giza, we explain how to choose the conduit size, how many wires can go in it by calculation, and when to choose anti-fire conduit.
What does a 16, 19 or 23 mm conduit mean?
Conduits in the Egyptian market are sold by nominal size, the most common being 11, 13, 16, 19, 23, 29 and 36 mm. What matters is knowing whether this number is the inner or the outer diameter, because the wires pass through the inner diameter:
- ✔ Some products state clearly in their name that the number is the inner diameter, such as Alaa El Din anti-fire conduits 16, 19 and 23 mm and Moustafa Mahmoud conduits 16 and 23 mm.
- ⚠ Other products state that the number is the outer diameter, such as sizes 20, 25 and 32 mm. Here the inner diameter is smaller: for example, a 20 mm outer-diameter conduit from one manufacturer has a stated inner diameter of 15.5 mm.
- ✔ If it isn't stated, ask or check the manufacturer's catalog before you calculate.
Types of electrical conduit: standard, flexible or anti-fire?
| Type | How to recognize it | Where it usually goes |
|---|---|---|
| Standard corrugated conduit (Pliable) | Corrugated plastic that bends by hand and keeps its shape | Inside walls and floors before plastering and screeding; the most used in apartments |
| Flexible conduit (Flexible) | Softer, bends and springs back, made for movement and short connections | Final connections to appliances and places that need flexibility |
| Anti-fire conduit (Anti-fire) | Its material does not propagate flame (Non-flame propagating) | False ceilings (gypsum board), enclosed spaces, and buildings where the specifications require it |
The international standard for conduit systems for cable management, IEC 61386 (Part 22 for pliable conduits and Part 23 for flexible ones), classifies conduit for fire into two types: flame propagating and non-flame propagating, and this classification is set by a 1 kW flame test per IEC 60695-11-2. So anti-fire conduit is not "never burns", but once the flame is removed it does not keep spreading it along the conduit.
- ⚠ Don't rely on the color or the name alone: check the label or the manufacturer's catalog and see whether it says non-flame propagating or compliance with IEC 61386.
- ✔ In a false ceiling specifically, the conduit is exposed and surrounded by air, so anti-fire is a much safer choice there.
How many wires fit in a 16, 19 or 23 mm conduit?
The rule we use comes from NEC Chapter 9 Table 1 (the US National Electrical Code, NFPA 70): the maximum fill of the conduit's inner area is 53% for one wire, 31% for two wires, and 40% for 3 or more wires. The wire outer diameter (with insulation) is taken at its maximum value from the datasheet of H07V-R stranded PVC-insulated copper wire (compliant with EN 50525-2-31): 1.5 mm² = 3.3 mm, 2.5 mm² = 4.0 mm, 4 mm² = 4.6 mm, 6 mm² = 5.2 mm, and 10 mm² = 6.7 mm.
How the calculation works
- Conduit inner area = 3.14 × (inner diameter)² ÷ 4. For example, a 16 mm inner-diameter conduit = about 201 mm², and 40% of that = about 80 mm².
- Area of a 2.5 mm² wire with insulation = 3.14 × 4.0² ÷ 4 = about 12.6 mm².
- 80 ÷ 12.6 = 6.4, so a maximum of 6 wires of 2.5 mm² in a 16 mm inner-diameter conduit.
This table is calculated the same way, and assumes the size is the inner diameter:
| Conduit (inner diameter) | 40% of the area | 1.5 mm² | 2.5 mm² | 4 mm² | 6 mm² | 10 mm² |
|---|---|---|---|---|---|---|
| 13 mm | 53 mm² | 6 | 4 | 3 | 1 | 1 |
| 16 mm | 80 mm² | 9 | 6 | 4 | 3 | 1 |
| 19 mm | 113 mm² | 13 | 9 | 6 | 5 | 3 |
| 23 mm | 166 mm² | 19 | 13 | 10 | 7 | 4 |
| 29 mm | 264 mm² | 30 | 21 | 15 | 12 | 7 |
- ⚠ These are maximum calculated numbers in a straight run, not a target to reach. Corrugated conduit has a ridged inner surface, and bends and long distances make pulling harder, so leave more room.
- ⚠ If the number on the conduit is the outer diameter, the table doesn't apply; calculate with the inner diameter stated in the manufacturer's catalog.
- ⚠ The more loaded wires in the same conduit, the lower the wire's current-carrying capacity (the grouping effect). This may lead the electrician to increase the wire size or split the circuits across more than one conduit. Read our guide to breakers and wire sizes.
- ✔ If you want a more precise number for a specific conduit, refer to the manufacturer's table that sets the number of wires for each size.
Which conduit size should I choose for each circuit in the apartment?
This is a practical application of the table, with standard wires (line + neutral + earth = 3 wires per circuit):
| Use | Wires | Comfortable conduit (inner diameter) |
|---|---|---|
| Lighting circuit | 3 × 1.5 mm² | 16 mm (13 mm is possible for short runs) |
| Standard socket circuit | 3 × 2.5 mm² | 16 mm |
| AC or water heater line on 4 mm² | 3 × 4 mm² | 19 mm (16 mm is enough by calculation, but 19 is easier to pull) |
| Line on 6 mm² | 3 × 6 mm² | 19 or 23 mm |
| Two circuits in the same conduit (2.5 mm²) | 6 × 2.5 mm² | 19 or 23 mm instead of 16, which would be at the limit |
| 10 mm² feeder line (from the meter to the panel) | 3 × 10 mm² | 23 mm or larger depending on the distance and the electrician |
The wire size itself is set by the breaker and the appliance current, not by the conduit. If you're still unsure, see Which breaker amperage for your apartment?.
Common electrical conduit mistakes
- ⚠ One conduit for power and internet or satellite: keep power wires separate from internet, satellite and phone cables in separate conduits, for safety and to avoid interference.
- ⚠ Many sharp bends without a junction box: the more bends, the harder the pull and the insulation can get damaged. Add junction boxes on long runs and at changes of direction.
- ⚠ A narrow conduit for the AC line: a 4 or 6 mm² wire in a 13 mm conduit is at the limit or beyond. Make it 19 mm.
- ⚠ Overfilling the conduit to save money: it makes replacing wires harder later and raises the wire temperature.
- ✔ Pull the wire after the conduit is fixed and, before plastering, make sure pulling is easy; leave a draw wire in spare conduits.
- ✔ An empty spare conduit for each room saves a lot of wall breaking if you want to add a point later.
⚠ Safety note: planning conduit routes and pulling and connecting wires must be done by a qualified electrician or electrical engineer, and any work on a live circuit must be done after switching off the supply and confirming with a tester that there is no voltage. The tables here are a planning guide, and the electrician confirms the final size according to the manufacturer's table and the Egyptian Code for Electrical Installations.
Electrical conduits available on Tawredaat
Alaa El Din standard conduits
Alaa El Din anti-fire conduits (inner diameter)
- Alaa El Din anti-fire conduit 16 mm - 45 m
- Alaa El Din anti-fire conduit 19 mm - 45 m
- Alaa El Din anti-fire conduit 23 mm - 45 m
Moustafa Mahmoud PE conduits
- Moustafa Mahmoud conduit 16 mm inner diameter - 45 m
- Moustafa Mahmoud conduit 19 mm - 45 m
- Moustafa Mahmoud conduit 23 mm inner diameter - 45 m
You can see all sizes in our electrical conduits collection, flexible conduits collection and all pipes and conduits, and breakers in our breakers collection. And when you reach the finishing stage, see our guide to choosing switches and sockets.
Frequently asked questions
What conduit size do I need for an apartment?
Usually 16 mm inner diameter for lighting and standard socket circuits, and 19 or 23 mm for AC and water heater lines on 4 or 6 mm² or when more than one circuit shares the same conduit. The electrician confirms based on the route.
How many 2.5 mm² wires fit in a 16 mm conduit?
By calculation, a maximum of 6 wires if 16 mm is the inner diameter, at 40% fill (NEC Chapter 9 Table 1) and a wire diameter of 4.0 mm. In practice keep it lower so pulling stays easy.
What is different about anti-fire conduit?
Its material is classified as non-flame propagating (per IEC 61386), so if a spark or small fire happens it does not keep spreading it along its length. This matters especially in false ceilings and enclosed spaces.
Is a 20 mm conduit the same as 19 mm?
Not necessarily. Most 20, 25 and 32 mm sizes are stated as outer diameter, so the inner diameter is smaller (for example 15.5 mm in a 20 mm outer-diameter conduit from one manufacturer). Check what is stated in the product name or the catalog.
Can I put the internet cable with power wires in the same conduit?
Better not. Keep them in separate conduits for safety and to avoid interference with the internet and satellite signal.
Should I choose flexible or standard conduit?
Standard corrugated (pliable) conduit for rough-in inside the wall and floor, and flexible conduit for short connections that need movement.
Wiring your apartment?
Alaa El Din and Moustafa Mahmoud standard and anti-fire conduits in 16, 19 and 23 mm, with delivery in Cairo and Giza.
About Tawredaat: Tawredaat (توريدات) is an Egyptian supplier of electrical and finishing materials, serving homeowners, companies and contractors in Cairo and Giza. Questions? See our FAQ.
