How to read this AWG to amps chart
Every row pairs an American Wire Gauge size with the nominal copper cross-section it
actually contains, in mm², and with four current ratings. The gauge number alone tells you
nothing about how much current a wire can carry — the copper area does, and that is why the
mm² column sits second, right next to the gauge.
Copper area, not outside diameter
Flexible silicone wire is sold by its outside diameter far more often than by its conductor.
A cable advertised as 8 AWG may measure 8 mm across the jacket and hold barely
6 mm² of copper. Size from the strand count and strand diameter on the datasheet, then
compare that area against the chart. The calculator above does exactly this arithmetic.
The 60 °C and 200 °C columns
The 60 °C columns are the conservative everyday reference: the conductor stays cool,
terminals stay within their own ratings, and there is margin for a hot day. The 200 °C
columns are the thermal limit of the silicone insulation, not a design target. A conductor
run at its 200 °C limit will melt heat-shrink, discolour terminals and burn skin on
contact, so use it only to understand the headroom you have, never as the number you design to.
Maximum load — where the current type really shows
The ampacity columns are in amperes, and amperes are amperes: a conductor does not care
whether the heat came from DC or AC. What changes completely is what those amperes are
worth. The same 0 AWG conductor at its 109.7 A rating delivers
2.6 kW on a 24 V DC system, 13.2 kW on
120 V single-phase, and 36 kW on 208 V three-phase — a
factor of fourteen, from voltage and the √3. On a 230/400 V system the spread is
wider still, at twenty-nine.
Read the other way round, that is the number most people actually want: for a given load,
the current you must carry is wildly different between DC and AC, and the copper you need
follows the current, not the watts. A 3 kW load is 125 A at 24 V DC and
8.3 A at 208 V three-phase.
Resistance and maximum run
The last two columns are the ones the current-type toggle moves most. Resistance is
ρ/A per metre, switching to the AC value at your chosen frequency. Maximum run is
the longest one-way length that keeps the drop within 3 % while the conductor carries
its ≤3 conductor 60 °C current, at the voltage set in the calculator.
That last column is worth staring at. The same 0 AWG conductor is good for
9.6 m on a 24 V DC system and 105 m on
208 V three-phase — a factor of eleven, from voltage and the √3 alone, with the
copper completely unchanged. Ampacity is rarely what limits a long run; voltage drop is.
Bundled versus free air
A single conductor hanging in still air sheds heat in every direction. The same conductor in
the middle of a loom shares its heat with its neighbours, and all of them run hotter. The
≤3 conductors columns assume a normal cable or small bundle; the
free air columns assume one conductor with nothing around it. Anything above
three current-carrying conductors needs the grouping factors in the calculator on top.
How the wire gauge calculator works
The calculator starts from the physical construction of the wire rather than from its label,
then walks the same four steps an engineer would.
1. Cross-section from strand count
Copper areaA = n × π × d² / 4
n is the number of strands and d is the diameter of one
strand in millimetres. A typical 4 AWG silicone lead of 1 650 strands at
0.08 mm works out to 8.29 mm² — well under the 21.15 mm² a real 4 AWG
conductor carries, which is exactly the kind of mismatch this page exists to catch.
2. Equivalent AWG
Gauge from areaAWG = 36 − 39 × log(deq / 0.127) / log(92)
The area is converted back to an equivalent solid diameter, then to a gauge number on the
AWG scale. The result is usually fractional, which is honest: real stranded wire rarely
lands exactly on a gauge.
3. Ambient and grouping derating
Derated ampacityI = Ibase × kambient × kgrouping
Base ampacity comes from your own cross-section, not from whichever row is closest:
between two tabulated gauges the current follows a power law in area,
I ∝ Ak, with k taken from that pair of rows
— 0.5 to 0.7 here, because heat arrives through a section and leaves through a surface. Land
exactly on a gauge and you get the published figure back. The ambient factor is interpolated between
the published correction points — 60 °C conductors lose capacity quickly above
30 °C, while 200 °C conductors keep working far into the heat. The grouping factor
comes from the installation selector, and the two multiply.
4. Voltage drop and wire loss
Direct current, and single-phase ACΔU = 2 × I × R × L × cos φThree-phase AC, line to lineΔU = √3 × I × R × L × cos φ
R is the resistance per metre, ρ/A, with ρ = 0.0175 Ω·mm²/m
for copper at 20 °C, and L is the one-way run. Direct current and single-phase
AC both travel out and back, so the length counts twice. A three-phase circuit does not:
the line-to-line drop carries a √3 instead. Power factor is 1 for DC, which is why the
first formula collapses to the familiar 2IRL.
Power lost as heat is I²R per conductor — two conductors for DC and
single-phase, three for three-phase. On low-voltage systems this, not ampacity, is usually
what forces a bigger conductor: a 12 V circuit allows only 0.36 V of drop at the
common 3 % target.
Reactance is left out. For the cross-sections and run lengths this page covers it sits well
below the uncertainty in the resistance itself, but on long three-phase runs in conduit it
stops being negligible and you should size from the cable's published R and X.
5. Why three-phase derates, and why frequency mostly does not
Two separate things are at work, and they are wildly different in size.
Conductor count is the big one. A three-phase circuit puts three
current-carrying conductors in the cable where DC and single-phase put two. Three
conductors each dissipating I²R make half again as much heat in the same
bundle, so each one has to be rated lower. IEC 60364-5-52 handles this by publishing
separate 2 loaded conductors and 3 loaded conductors columns; across its
copper tables the ratio averages 0.915, and that is the factor applied to
the in-cable columns here. It is a frequency-independent, roughly 9 % cut — the reason
0 AWG reads 109.7 A on DC and 100.4 A on three-phase. The free-air columns
describe one isolated conductor, which is the same object in every mode, so they do not
move.
Frequency is the small one, at least at mains. Alternating current pushes
charge toward the conductor surface, so resistance rises — but in copper at 60 Hz the
skin depth is about 8.5 mm, while even a 0 AWG conductor has a radius of only
4.1 mm.
Skin and proximity, IEC 60287-1-1ys = xs⁴ / (192 + 0.8 xs⁴)yp = ys (d/s)² [0.312 (d/s)² + 1.18 / (ys + 0.27)]
Both effects are counted — skin, plus the proximity effect of neighbouring conductors, which
dominates once you leave mains frequency. Together they come to 0.40 %
at 60 Hz for 0 AWG, 0.06 % at 4 AWG and nothing measurable below that.
This is the entire difference between DC and single-phase AC here: both have two loaded
conductors, and unarmoured low-voltage wire has no sheath or dielectric losses to add. The
table shows a decimal place so you can see it on the gauges where it exists — 0 AWG
goes from 109.7 A to 109.5 A — and read as identical where it genuinely is. Ampacity scales as
1/√(1+ys), so it moves by well under a tenth of a percent — far less than the
spread between one manufacturer's datasheet and another's. So the frequency term alone would not justify a
separate AC column; the conductor count is what does.
It does start to matter higher up. At 400 Hz — aircraft and some drive systems —
0 AWG picks up 17 %, which is why the calculator takes a frequency rather than
assuming mains. The published fit holds to xs ≤ 2.8, roughly 1 kHz
on the largest gauge here; above that the calculator flags its own result as indicative.
Conductor materials
AWG is a geometric size, so the cross-section in the table is the same whatever the metal
is. What changes is how much current that cross-section can carry and how much voltage it
drops. Both follow from one number — conductivity, quoted on the IACS scale where annealed
copper is 100 %.
Ampacity against copperI / ICu = √(σ / σCu)Resistance against copperR / RCu = σCu / σ
Identical geometry and an identical permitted temperature rise mean I²R is
fixed, so current goes as the inverse square root of resistivity. That is not a rule of
thumb: against NEC 310.16 the aluminium-to-copper ratio averages 0.774
from 6 AWG to 4/0, where √0.612 predicts 0.782.
What the selector offers
- Copper
- 100% IACS · ×1.000
- Silver
- 105% IACS · ×1.025
- Tinned copper
- 96% IACS · ×0.980
- Nickel-plated
- 95% IACS · ×0.975
- Aluminium 1350
- 61.2% IACS · ×0.782
- Alloy 8000
- 61% IACS · ×0.781
- Copper-clad alu
- 61.5% IACS · ×0.784
- Copper-clad steel
- 30% IACS · ×0.548
Anything else goes in as a custom % IACS, which is the honest way to handle a datasheet
that quotes its own figure.
Plated coppers
Plating is about the environment, not conduction. Tin resists corrosion and keeps solder
wetting; nickel survives past 200 °C where tin has long melted; silver is for RF, where
current rides the surface. The penalty is small and depends on how thick the coating is
relative to the strand: on a 0.08 mm strand a micron of tin occupies roughly 5 % of
the area and conducts at 15 % of copper, which is where the 96 % figure comes from.
On thicker strands it is less. Silver plating does not change DC resistance measurably,
since the bulk is still copper.
Aluminium, and what it costs you
Aluminium carries about 78 % of copper's current at the same size, so matching a copper
conductor takes 1.64× the area — roughly two AWG sizes up. It is still worth
it on long runs, because it is around a third of the weight for the same conductance and
much cheaper.
The catch is never the metal, it is the joint. Aluminium creeps under clamping pressure, so
a terminal that was tight last year may not be now; it grows an insulating oxide the moment
it meets air; and it expands about 40 % more than copper with temperature, working
itself loose through every heating cycle. Aluminium branch circuits earned their reputation
in the 1960s and 70s for exactly this. Use terminals listed for aluminium, apply
anti-oxidant compound, torque to the figure on the connector, and never put bare aluminium
against bare copper in a damp place — the galvanic pair eats the aluminium.
Fine-stranded silicone wire, which is what this page is mostly about, is not made in
aluminium: it does not survive the flex cycles.
Copper-clad conductors
Copper-clad aluminium is aluminium with a copper skin, typically 10 % by volume. It
terminates like copper and conducts like aluminium, which is a reasonable trade — the
problem is that it is frequently sold as copper. Strip a sample: the core is
silver-coloured. Copper-clad steel is a different animal at 30 % IACS, made for
mechanical strength and RF skin conduction, not for carrying power; a magnet identifies it
instantly.
One caveat on temperature
Every figure here is at 20 °C. A conductor actually running at 60 °C has around
16 % more resistance, and aluminium's temperature coefficient (0.00403/K) is slightly
worse than copper's (0.00393/K). For voltage drop on a hot circuit, add that margin
yourself — the calculator does not, because it would need a conductor temperature rather
than an ambient one.
Insulation
Insulation contributes one thing to ampacity: how hot it will let the conductor get. Copper
does not care — it is happy at 400 °C. The plastic around it decides where you have to
stop, and that single number moves the high-temperature column of the table.
Ampacity at a different ratingI / I200 = √( (T−30) / (1 + α(T−20)) ) ÷ √( 170 / (1 + α·180) )
Heat leaves the conductor in proportion to ΔT while heat arrives as I²R,
and R itself climbs with temperature — which is why the gain from a hotter rating
is less than it first looks. Against NEC 310.16 this predicts the 90 °C to
60 °C ratio as 1.347 where the published columns give 1.333 to 1.360
for 10 AWG and larger. Silicone at 200 °C is the reference at exactly 1.000, so
selecting it reproduces the published data untouched.
What the selector offers
- PVC
- 70 °C · ×0.579
- PVC/nylon THHN
- 90 °C · ×0.687
- XLPE / EPR
- 90 °C · ×0.687
- PVC, heat-resistant
- 105 °C · ×0.751
- ETFE (Tefzel)
- 150 °C · ×0.893
- Silicone
- 180 °C · ×0.962
- Silicone, FEP
- 200 °C · ×1.000
- PTFE / PFA
- 260 °C · ×1.090
The rule that catches people out
The whole circuit runs at the temperature of its weakest part, and that is almost
never the wire. A breaker terminal listed for 75 °C caps the whole run at
75 °C no matter what the insulation says — NEC 110.14(C) makes this explicit, and
most equipment under 100 A is listed at 60 °C. Buying 200 °C silicone and
sizing from its 200 °C column, then landing it in a 75 °C lug, is how connections
cook. This is exactly why the conservative 60 °C column stays fixed in this table
regardless of what you select: for most real installations it is the number that governs.
The high-temperature rating buys you margin in a hot enclosure, survival next to an exhaust
or a heater, and the ability to run at full current when the ambient is already 80 °C.
It does not license you to push more current through the same terminals.
Choosing between them
PVC is cheap, tough against abrasion and stiff in the cold; it softens
where it is hot and gives off hydrogen chloride in a fire, which is why LSZH compounds
replace it in tunnels and ships. XLPE is PVC's crosslinked cousin: same
price bracket, better heat, does not melt and flow. Silicone is the most
flexible thing on the list by a wide margin and survives 200 °C, but it tears and
abrades easily, so it wants a sleeve wherever it can rub. PTFE and PFA are
the best electrically and thermally and shrug off almost every solvent, at several times
the price and with noticeably less flexibility. ETFE is the compromise the
aerospace world settled on: thin wall, tough, 150 °C.
Two things this does not model
Wall thickness. A thick jacket is a thermal blanket, so two 90 °C cables of different
construction do not carry the same current. Datasheets rarely publish thickness in a
comparable way, so only the rating is used here.
Voltage rating, which is a separate property entirely. 600 V, 1 kV and 3 kV
versions of the same insulation share a temperature rating and differ only in wall. Check it
separately — nothing on this page tells you whether the insulation will hold your voltage.
AWG to mm² at a glance
Nominal copper cross-sections per ASTM B258, with the nearest metric cable size the
market actually sells against each one.
- 0 AWG
- 53.49 mm² · ≈ 50 mm²
- 2 AWG
- 33.62 mm² · ≈ 35 mm²
- 4 AWG
- 21.15 mm² · ≈ 25 mm²
- 6 AWG
- 13.30 mm² · ≈ 16 mm²
- 8 AWG
- 8.37 mm² · ≈ 10 mm²
- 10 AWG
- 5.26 mm² · ≈ 6 mm²
- 12 AWG
- 3.31 mm² · ≈ 4 mm²
- 14 AWG
- 2.08 mm² · ≈ 2.5 mm²
- 16 AWG
- 1.31 mm² · ≈ 1.5 mm²
- 18 AWG
- 0.823 mm² · ≈ 1 mm²
- 20 AWG
- 0.518 mm² · ≈ 0.5 mm²
- 22 AWG
- 0.326 mm² · ≈ 0.35 mm²
The right-hand figure is the size a supplier will usually quote. It is almost always larger
than the true AWG area, so a metric cable labelled as an AWG equivalent is safe on ampacity
and misleading on price per millimetre of copper.
Frequently asked questions
How many amps can each AWG wire size carry?
For tinned copper conductors at 30 °C ambient, the conservative 60 °C reference in the chart above gives roughly 7.8 A for 18 AWG, 13.7 A for 14 AWG, 25.5 A for 10 AWG, 34.3 A for 8 AWG, 60.7 A for 4 AWG and 109.7 A for 0 AWG with up to three current-carrying conductors in a cable. A single conductor in free air runs cooler and carries more. High-temperature silicone wire rated to 200 °C carries roughly twice the conservative figure, but only if every terminal, fuse and connector in the circuit is rated for that temperature too.
What is the difference between the 60 °C and 200 °C columns?
Both describe the same copper. The difference is how hot you allow the conductor to get. The 60 °C columns are the everyday design baseline: the wire stays touch-safe and the insulation, terminals and adjacent materials are comfortable. The 200 °C columns are the thermal limit of the silicone insulation itself — the current at which the conductor reaches 200 °C. Treat the second number as a ceiling for short, well-ventilated runs, not as a design target.
How do I convert AWG to mm²?
AWG is a logarithmic scale, so there is a closed formula rather than a simple ratio. The conductor diameter in millimetres is d = 0.127 × 92(36−AWG)/39, and the cross-section is A = π d²/4. In practice, every three AWG steps roughly double the copper area, and six steps roughly double the diameter. The mm² column in the chart above already carries the ASTM B258 nominal values, so you can read the conversion straight off the table.
Why is 25 mm² wire sold as 4 AWG?
Because it is a marketing label, not a measurement. True 4 AWG is 21.15 mm² of copper. Sellers of flexible silicone wire frequently round up to the nearest metric size, or quote the outside diameter over the insulation instead of the conductor. Always size from the strand count and strand diameter on the datasheet — that is what the calculator on this page asks for — and treat any headline mm² figure as unverified until it matches.
Does a higher strand count increase ampacity?
Not by itself. Ampacity follows the total copper cross-section, so 1 650 strands of 0.08 mm carry the same current as a solid conductor of the same area. What fine stranding buys you is flexibility, vibration and flex-cycle life, and easier routing in tight enclosures. At DC and mains frequencies the skin effect is negligible at these sizes, so stranding gives no measurable current bonus.
How do I calculate DC voltage drop?
Voltage drop is the load current times the resistance of the full circuit — out and back. With copper resistivity ρ = 0.0175 Ω·mm²/m, the drop is ΔU = I × ρ × 2L / A, where L is the one-way run length. Most low-voltage DC systems aim to keep the drop under 3 % of system voltage; on a 12 V circuit that is only 0.36 V, which is why long 12 V runs are usually sized by voltage drop rather than by ampacity.
How much should I derate for bundled conductors?
Bundling traps heat, so every conductor in the group carries less. Common factors are 80 % for 4–6 current-carrying conductors, 70 % for 7–9, 50 % for 10–20, 45 % for 21–30, 40 % for 31–40 and 35 % beyond that. Ambient temperature derates on top of grouping, and the two multiply. Conductors that never carry current at the same time, and neutrals in a balanced circuit, usually do not count towards the group.
Can I use this chart for aluminium wire?
Yes — switch the conductor material and every column recalculates. Aluminium at 61.2 % IACS carries about 78 % of copper's current at the same cross-section, because ampacity follows the square root of conductivity. Matching a copper conductor therefore takes 1.64 times the area, roughly two AWG sizes up. The arithmetic is the easy part: aluminium creeps under clamping pressure, oxidises on contact with air and expands more than copper when hot, so it needs terminals listed for aluminium, anti-oxidant compound and a torque wrench. Copper-clad aluminium behaves the same electrically while terminating like copper, and copper-clad steel at 30 % IACS is for strength and RF, not for power.
Does the ampacity change between DC and AC?
Not meaningfully at mains frequency. Alternating current crowds toward the conductor surface, but the skin depth in copper is about 9.4 mm at 50 Hz and 8.5 mm at 60 Hz, while a 0 AWG conductor has a radius of just 4.1 mm. By IEC 60287 the resistance rise works out at 0.08 % for 0 AWG and under 0.01 % below 4 AWG, so the same table serves DC, single-phase and three-phase. What the current type really changes is the voltage drop: two conductors out and back for DC and single-phase, √3 line-to-line for three-phase, with the power factor on top. Skin effect only becomes worth counting in the hundreds of hertz, which is why the calculator asks for a frequency.
Is this chart the same as NEC or IEC ampacity?
No. This is a reference for flexible, fine-stranded tinned copper lead wire with silicone insulation, of the kind used in equipment wiring, battery leads, robotics and RC. Building installations are governed by NEC 310 tables in North America and IEC 60364-5-52 in Europe, which assume different insulation, installation methods and correction factors. Use those codes for fixed wiring, and use this chart for equipment and appliance wiring.
Read the source, or fix it
This page is open source. The table data, both translations, the calculator and
this text are all produced by one generator, which is why the English and
Ukrainian versions cannot drift apart.
- src/build.php — the ampacity table, the copy, the FAQ and the JSON-LD
- src/template.html — the page shell and the calculator
- src/test.js — checks that run the calculator against the built pages
Found a wrong number, or want a gauge added? Open an issue or send a pull request
at github.com/66Ton99/homepage. Corrections backed by a
datasheet or a standard are especially welcome — the AWG 24–30 rows are the
shakiest, since they are indicative for fine-stranded silicone wire rather than
taken from a single authoritative table.