Pakistan wire size chart: SWG strand codes to mm²

The chart: every strand code in mm²

This is the table to keep. Read across: the code the shop quotes, the copper it actually contains, the metric size it is billed as, and what that size carries.

In Pakistan a wire is ordered by a strand code — 3/.029, 7/.029, 7/.036, 7/.044, 7/.052, 7/.064, 19/.052 — which states how many strands the conductor has and how thick each strand is, in thousandths of an inch. Multiply π/4 by the strand diameter in millimetres squared, then by the strand count, and the conductor's cross-section falls out: 7/.036 computes to 4.60 mm² and is sold as 4 mm²; 7/.064 computes to 14.53 mm² and is sold as 16 mm²; 19/.052 computes to 26.03 mm² and is sold as 25 mm². The code describes the geometry; the metric size decides which IEC 60228 resistance row and which BS 7671 current-capacity row apply. The two agree only approximately, so size the circuit against the smaller of the two areas and confirm the conductor by its resistance in ohms per kilometre.

How to read a strand code

There is one formula behind the whole chart: area = strands × π/4 × (strand diameter in inches × 25.4)². Worked through on 7/.036, the size most asked for at an AC point:

The same five steps on the largest common code, 19/.052: 0.052 × 25.4 = 1.3208 mm; 1.3208² = 1.7445; π/4 × 1.7445 = 1.3701 mm² per strand; × 19 = 26.03 mm², sold as 25 mm². Note that 7/.052 and 19/.052 share a strand — the only difference is how many of them are laid up. That is why the 25 mm² conductor is not quite three times the 10 mm² one: 19 ÷ 7 = 2.71.

Does the code reach the size it is sold as?

IEC 60228 does not define a conductor by its area. It defines it by a maximum resistance per kilometre, because resistance is what can be measured on a finished coil. So the fair test of a strand code is to convert its computed area into a resistance and hold it against the limit for the metric size on the label.

Four of the seven codes clear their metric limit comfortably. One is marginal and two do not reach it on geometry alone. That is not a scandal and it is nobody's fault — it is what happens when an imperial naming system from the 1950s is mapped onto metric standard sizes. The practical rule that follows is simple, and it is the reason this page exists:

• 3/.029 is a lighting wire. At 1.28 mm² it belongs on lamp and fan points behind a 6 or 10 A way. Putting it on a socket circuit because "3/.029 is 1.5 mm²" is where the arithmetic starts to matter.
• 7/.064 is short of a true 16 mm² by about 9% on area. On a house submain that margin is usually absorbed by the breaker below it; on a run near its thermal or volt-drop limit, step up to 25 mm² rather than assume the round number.
• Pilone labels by the same market convention. Our 7/.036 is billed as 4 mm² and our 7/.064 as 16 mm², exactly as the trade does, and both numbers are printed above so you can size against either. We publish the computed area beside the nominal on every strand-code page rather than only the flattering one.
• Ask for the resistance, not the adjective. "Full gauge" is a claim. Ohms per kilometre, measured on the coil in front of you, is a fact.

Is 7/.029 really an SWG size?

The trade calls these SWG sizes, and everyone knows what is meant, but strictly the codes are not gauge numbers. Standard Wire Gauge is a numbered ladder — SWG 16, SWG 20 — where each number stands for a fixed diameter in inches. A Pakistani cable code quotes the diameter itself. Two of the common strand diameters land exactly on an SWG number; the rest sit between gauges.

This matters for one reason only: when someone converts a Pakistani code through an American AWG table, the answer comes out wrong. AWG is a different ladder again, and a strand code is not a gauge number in either system. Convert the way this page does — strands, diameter, area — and the answer is arithmetic rather than lookup.

25mm and 2.5mm are not the same cable

Retail listings across the country drop the decimal point: 2.5 mm² gets written and slugged as "25mm". Meanwhile 25 mm² is a real and completely different size — roughly ten times the copper. The two get confused in searches, in slugs, and occasionally on site, and that last one is a safety problem rather than a spelling one.

Three checks settle it before anyone cuts anything. Ask for the strand code: 7/.029 is the 2.5 mm², 19/.052 is the 25 mm². Ask for the amps: 27 A against 112 A is not a rounding difference. Lift the coil: one core of 25 mm² over 90 m holds ten times the copper of the 2.5 mm², and no listing can disguise that in the hand.

Our own flexible-cable listings carry the decimal-dropped form from an older catalogue run, so where you see "25mm" in a flexible-cable URL on this site the product is 2.5 mm². The true 25 mm² sizes sit in the standard range. Take 2.5mm² flexible cable for the small one and 25mm 4 core standard cable for the large one, and the 25mm vs 4mm comparison if the job sits between them.

Quick chooser: which code for which job

Starting points for a 220 V single-phase house on a WAPDA or K-Electric supply, before the run length and the installation method are checked. Every one of them can move up a size on a long run or a hot conduit; none of them should move down.

Two corrections are worth applying by hand before you order. Ambient first: the tabulated figures assume 30°C, and a roof void or a surface run in a Lahore June does not sit at 30°C, so the capacity comes down. Length second: multiply the millivolts per amp per metre from the chart by your current and your one-way run, and hold the answer under 2.5% of 230 V — 5.75 V — on a final circuit. The cable size calculator and the voltage drop calculator do both sums with your own figures; three-phase sizing and single-phase sizing take them further.

Check a coil by its weight

Copper has a fixed density, so a conductor of a given area has a fixed mass per kilometre: area in mm² × 8.89 kg/km. That gives any buyer a check that needs no laboratory. A 90 m coil of single-core 7/.036 built to the 4 mm² nominal holds 35.6 kg/km × 0.090 km = 3.20 kg of copper; built to the code's own 4.60 mm² geometry it holds 40.9 × 0.090 = 3.68 kg. Insulation, sheath and the drum sit on top of both figures.

Use it as a floor, not as a verdict. A coil that weighs close to the figure tells you the copper is there; a coil well under it tells you either the conductor is thin or the coil is short, and the weight alone will not say which. The definitive test is still resistance measured end to end against the IEC 60228 limit for the size. Because a coil is not a fixed quantity in this market, the price per metre page shows how to convert a coil quote into a rate you can compare, and the cable price list holds the size ladder.

The same codes on aluminium

Aluminium cable is sold under the same codes, which is why a listing may read 19/.052″ (25 mm²) 4 core aluminium. The geometry is identical — 19 strands of 0.052 inch is 26.03 mm² whatever metal it is drawn from. What changes is what that area carries, because aluminium conducts less well than copper. In the market aluminium is often called "silver cable", after its colour; it is aluminium, not silver, and no silver is involved.

Read across one row and the trade-off is plain: 25 mm² aluminium carries 87 A where 25 mm² copper carries 112 A. To match a copper size on amps, one aluminium size up is enough at the small end — 16 mm² aluminium at 66 A covers 10 mm² copper at 63 A, and 25 mm² aluminium at 87 A covers 16 mm² copper at 85 A. From 25 mm² copper upward it takes two: 35 mm² aluminium stops at 107 A, so matching 112 A means 50 mm². On a long service drop that is still the cheaper metal by a wide margin; on a 4 mm² appliance tail it is the wrong choice. See 10mm 2 core aluminium, 16mm 2 core aluminium and 25mm² aluminium cable, or the copper vs aluminium comparison for the full argument.

7/.036 kitne mm ka hota hai?

7/.036 ka matlab hai saat taar, har taar 0.036 inch mota. Hisaab yeh hai: 0.036 × 25.4 = 0.9144 mm, phir π/4 × 0.9144² = 0.6567 mm² ek taar ka, aur saat taar mila kar 4.60 mm². Market mein yehi wire 4 mm² ke naam se bikta hai. 1.5 ton AC point ke liye yehi size chahiye, apne alag 20 A MCB par — tafseel 1.5 ton AC wire size guide mein hai.

Aur 25mm aur 2.5mm ek cheez nahi hain. 2.5 mm² yaani 7/.029 — 27 amp, kamre ke socket circuit ke liye. 25 mm² yaani 19/.052 — 112 amp, meter se DB tak main line ke liye. Area mein takreeban dus guna farq hai. Listing par sirf "25mm" likha ho to strand code poochein: 7/.029 hai to 2.5 mm² hai, 19/.052 hai to 25 mm².

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