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Electrical Load and MCB Calculator

Count your lights, fans, sockets and big appliances. Get the circuits, each MCB, the wire and the connected load.

Electrical● Free Formula shown
Quick Answer

Add up every light, fan, socket and appliance to get the connected load. Then split it into circuits by the CPWD rules: a lighting circuit takes at most 10 points and 800 W, a home power circuit takes two 16 A sockets, three 6 A sockets, or one 16 A with two 6 A, and anything over 1 kW (AC, geyser, induction) gets its own MCB. Each MCB is the next standard rating above its circuit's current, and the wire must carry at least the MCB. The 2BHK in example 1, with one AC and two geysers, comes to 10.04 kW connected across 10 circuits.

Figures checked Oct 2026. Source: CPWD General Specifications for Electrical Works, Part I (Internal), 2013: cl. 3.9 ratings of outlets, cl. 3.10 capacity of circuits, cl. 3.12 cables, cl. 3.3.2 (ix) spare outgoing ways (copy hosted by the Directorate General of Lighthouses and Lightships).

10 / 800 Wmost points and watts on one lighting circuit
2 × 16 Amost 16 A sockets on one home power circuit
60 Wdesign load of a ceiling fan (CPWD)
1 kWabove this, the appliance gets its own MCB

Guides: AC nameplate to MCB, 2BHK wiring plan checklist.

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The Formula

Circuits and MCBs = Connected load = Σ (points × watts); lighting circuits = smallest n with every circuit ≤ 10 points and ≤ 800 W; power circuits = fewest groups of 2 × 16 A, 3 × 6 A or 1 × 16 A + 2 × 6 A; one circuit per appliance over 1 kW; circuit current IB = W ÷ V (AC: nameplate amps); MCB = smallest standard rating ≥ IB and ≥ the largest socket on it; wire = smallest size with IS 3961 rating × 1.23 ≥ MCB, at least 1.5 sq mm (light) or 4 sq mm (power)

Outlet ratings and circuit limits are CPWD General Specifications for Electrical Works, Part I (Internal), 2013, clauses 3.9, 3.10 and 3.12. MCB ratings are the preferred values in IS/IEC 60898-1:2002 clause 5.3.2. The rule that the MCB sits between the load current and the wire's rating is IS 732:1989 clause 5.3.3.2, with wire ratings from IS 3961 (Part 5):1968 Table 1 and the 1.23 MCB factor from its Table 8.

How a 2BHK becomes 10 circuits (worked example 1)14 lights at 10 W and 5 fans at 60 W make 19 points and 440 W, so 2 lighting circuits; 3 sixteen-amp and 10 six-amp sockets make 5 power circuits; 1 AC and 2 geysers get 3 circuits; total 10 circuits and 10.04 kW.1Lights and fans19 points, 440 W → 2 lighting circuits2Sockets3 × 16 A + 10 × 6 A → 5 power circuits3Big appliances1 AC + 2 geysers → 3 own circuits4Total10 circuits, 10.04 kW connected
How a 2BHK becomes 10 circuits (worked example 1). The calculator's steps for the default inputs.

Assumptions

  • Single-phase 230 V circuits, copper wire in conduit at 40 °C, one circuit per conduit. If several circuits share a conduit or a roof slab runs hot, check each wire with the wire size calculator.
  • Light points are counted at the lamp's own watts (CPWD cl. 3.9 ii). CPWD lets a lighting circuit take more than 10 points when the lamps are small; this calculator keeps the 10-point limit.
  • 6 A sockets go on power circuits, three to a circuit, as CPWD cl. 3.10 (iii) allows in homes. Some electricians put a few 6 A sockets on the lighting circuits instead; that is their call.
  • An MCB is never below the rating of the biggest socket on its circuit, so a plug the socket accepts does not trip it. This one rule is our own choice; neither CPWD nor the IS codes state it.
  • Every AC, geyser and other appliance you enter gets its own circuit. The AC's current comes from its nameplate, because a compressor's power factor is below 1.
  • The connected load assumes everything runs at once. IS 732 cl. 3.1.2 allows for diversity when sizing the main supply, but gives no figure, so none is applied here.
  • We quote the editions on the free public copies: CPWD General Specifications Part I (Internal) 2013, IS 732:1989 (revised 2019), IS 3961 (Part 5):1968 and IS/IEC 60898-1:2002. Check the current edition before you rely on a clause.
CPWD design loads, against the 800 W lighting circuit limitCeiling fan 60 W, 6 A socket 100 W, 16 A socket 1,000 W; reference line at 800 W.Ceiling fan60 W6 A socket100 W16 A socket1,000 W800 W lighting limit
CPWD design loads, against the 800 W lighting circuit limit. A 16 A socket alone counts for more than a whole lighting circuit may carry.

What goes on each circuit (CPWD 2013)

The limits this calculator packs your points into, from CPWD General Specifications for Electrical Works, Part I (Internal), 2013.

CircuitWhat it may feedDesign loadMinimum wire
LightingLights, fans and call bells: at most 10 points and 800 W (cl. 3.10 i)Fan 60 W; other lamps at their own watts (cl. 3.9)1.5 sq mm (cl. 3.12)
Power, home2 × 16 A sockets, or 3 × 6 A, or 1 × 16 A + 2 × 6 A (cl. 3.10 iii)16 A socket 1,000 W; 6 A socket 100 W, unless the real load is known (cl. 3.9 iii)4 sq mm (cl. 3.12)
Power, non-homeOne socket per circuit (cl. 3.10 ii)As above4 sq mm (cl. 3.12)
Any load over 1 kWIts own suitably rated MCB (cl. 3.10 iv)The appliance's own ratingBy calculation (cl. 3.12)

Read from the CPWD 2013 text on 10 October 2026. Standard MCB ratings from IS/IEC 60898-1:2002 cl. 5.3.2: 6, 8, 10, 13, 16, 20, 25, 32, 40, 50, 63, 80, 100 and 125 A.

Where the 10.04 kW comes from (worked example 1)Lights and fans 440 W, 6 A sockets 1,000 W, 16 A sockets 3,000 W, AC 1,600 W, two geysers 4,000 W.Lights and fans440 W6 A sockets1,000 W16 A sockets3,000 WAC1,600 W2 geysers4,000 W
Where the 10.04 kW comes from (worked example 1). Lights and fans are a small share. Geysers and 16 A sockets carry most of the load.

Worked Examples

When an MCB trips at once: B, C and D curvesType B trips above 3 and up to 5 times its rating, type C above 5 and up to 10 times, type D above 10 and up to 20 times.Type B3 to 5 × InType C5 to 10 × InType D10 to 20 × In
When an MCB trips at once: B, C and D curves. Upper end of each instantaneous trip range, in multiples of the MCB's rating (IS/IEC 60898-1 Table 2).

2BHK: 14 lights, 5 fans, 10 × 6 A and 3 × 16 A sockets, 1 AC, 2 geysers

  1. Lighting: 14 × 10 W + 5 × 60 W = 440 W on 19 points; 19 points need 2 circuits (10 points each at most)
  2. Circuit 1: 6 lights + 3 fans = 240 W; circuit 2: 8 lights + 2 fans = 200 W; both 6 A MCB on 1.5 sq mm
  3. Power: 1 × 16 A + 2 × 6 A (1,200 W), 2 × 16 A (2,000 W), then 8 × 6 A sockets in threes: 5 circuits
  4. Circuits with a 16 A socket get a 16 A MCB; the 6 A-only circuits get 6 A; all on 4 sq mm
  5. AC: 7.5 A from the nameplate → 10 A MCB; each geyser 2,000 ÷ 230 = 8.70 A → 10 A MCB
  6. Connected load 10,040 W = 10.04 kW; current if everything ran at once 44.20 A
  7. Answer: 10 circuits, so a 12-way board leaves 2 spare

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1BHK: 8 lights, 3 fans, 6 × 6 A and 2 × 16 A sockets, 1 geyser, no AC

  1. Lighting: 8 × 10 W + 3 × 60 W = 260 W on 11 points; 11 points need 2 circuits
  2. Circuit 1: 3 lights + 2 fans = 150 W; circuit 2: 5 lights + 1 fan = 110 W
  3. Power: 2 × 16 A on one circuit (2,000 W, 16 A MCB), 6 × 6 A in two threes (300 W each, 6 A MCB)
  4. Geyser: 8.70 A → 10 A MCB on 4 sq mm
  5. Connected load 4,860 W = 4.86 kW; current if everything ran at once 21.13 A
  6. Answer: 6 circuits, so an 8-way board leaves 2 spare

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3BHK: 24 lights, 8 fans, 16 × 6 A and 5 × 16 A sockets, 3 ACs, 2 geysers, a 2,500 W induction hob

  1. Lighting: 24 × 10 W + 8 × 60 W = 720 W, under 800 W, but 32 points need 4 circuits: points set the count here, not watts
  2. Each lighting circuit: 6 lights + 2 fans = 180 W
  3. Power: five circuits of 1 × 16 A + 2 × 6 A (1,200 W each, 16 A MCB), then 6 × 6 A in two threes: 7 circuits
  4. 3 ACs at 7.5 A → 10 A MCB each; 2 geysers → 10 A each; induction 2,500 ÷ 230 = 10.87 A → 16 A MCB
  5. Connected load 18,620 W = 18.62 kW; current if everything ran at once 82.59 A
  6. Answer: 17 circuits. A load this size raises the question of a three-phase supply; ask your electrician

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Tools on Amazon.in

Tools for checking the load

For seeing what your appliances really draw.

Hire a licensed electrician for any wiring work.

  • Reads real current draw to compare with the calculated load.AstroAI digital clamp meter (4.6★, 8,800 ratings) · See on Amazon.in
  • Checks voltage at the socket.AstroAI digital multimeter (4.5★, 54,500 ratings) · See on Amazon.in
  • Strips insulation cleanly without nicking the wire.Taparia WS 05 wire stripper (4.2★, 19,500 ratings) · See on Amazon.in
  • Measures cable runs between rooms.Stanley 5 m measuring tape (4.5★, 27,100 ratings) · See on Amazon.in

Or search Amazon.in yourself. Type what you need, or tap a common search.

clamp meterdigital multimeterwire strippermeasuring tape

As an Amazon Associate we earn from qualifying purchases. Ratings checked October 2026. We don't show prices; Amazon has the current one.

How to Use This Calculator

  1. Count the points. Walk the plan room by room and count light points, fan points, 6 A sockets and 16 A sockets.
  2. List the big appliances. Enter every AC, geyser and other appliance over 1 kW. Take the AC's watts and amps from its nameplate.
  3. Check the loads. Keep the CPWD defaults (fan 60 W, 6 A socket 100 W, 16 A socket 1,000 W) unless you know the real load.
  4. Read the circuits. The result gives the number of circuits, each MCB and wire, and the connected load. The table lists every circuit.
  5. Hand it to the electrician. Take the circuit table to your electrician before buying the board, the MCBs or the wire.

Tips and tricks

  • Count points from the furniture plan. A bed against a wall moves the socket, and a kitchen counter usually wants one more 16 A socket than you first think.
  • With LED lamps the 10-point limit fills long before the 800 W one. The third example needs 4 lighting circuits for 720 W.
  • Compressors draw a burst of current when they start. A C-curve MCB trips instantly only above 5 to 10 times its rating, a B-curve above 3 to 5 times, so ask which curve your electrician plans for the AC circuits.
  • Put each geyser and AC on its own MCB even if the room has a spare 16 A socket. CPWD wants anything over 1 kW on its own breaker, and a fault in the geyser then trips only its own MCB.
  • Buy the board after you've counted the circuits. Adding ways later means a new board; two spare ways cost little now.
  • Label every MCB on the board the day it is wired. In a fault at night, "Bedroom 2 sockets" is far quicker to find than "MCB 7".

What we would do

For a new flat, we'd count points from the furniture plan, keep the CPWD defaults for the sockets, and enter every AC and geyser at its nameplate rating. Then we'd take the circuit table, plus the wire size calculator's answer for any shared or hot conduit, to the electrician, and buy a board with at least two spare ways.

Frequently Asked Questions

How many points can go on one circuit?
Under CPWD's general specifications, a lighting circuit takes at most 10 points of lights, fans and call bells, and no more than 800 W. A power circuit in a home takes two 16 A sockets, three 6 A sockets, or one 16 A with two 6 A.
Which MCB for an AC?
The next standard rating above the AC's nameplate current, on its own circuit. A 7.5 A AC gets a 10 A MCB in this calculator. Compressors pull a burst at start-up, so ask your electrician whether to fit a C-curve MCB.
Which MCB for a geyser?
A 2,000 W geyser draws 2,000 ÷ 230 = 8.70 A, so the next standard rating is 10 A, on its own circuit. If the geyser plugs into a 16 A socket instead, the circuit gets a 16 A MCB.
What is connected load?
The sum of every light, fan, socket and appliance's rated watts, as if all ran at once. It is not the same as the sanctioned load your supply company sets, which follows its own rules.
How many ways should my distribution board have?
One outgoing way per circuit, plus spares. CPWD asks for reasonable spare ways; we'd leave at least two. The 2BHK in example 1 has 10 circuits, so a 12-way board.
What wire goes with each MCB?
The wire must carry at least the MCB's rating. CPWD sets 1.5 sq mm as the minimum for lighting and 4 sq mm for power circuits. For shared conduits or hot roofs, check each run with the wire size calculator.

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Sources & Limitations

What this calculator does not model

  • Single-phase only. It does not balance a three-phase supply or size the main cable from the meter.
  • No diversity is applied, so the connected load is the worst case, not the demand the supply company plans for.
  • Each wire assumes one circuit alone in a conduit at 40 °C. Shared conduits and hot slabs need the wire size calculator.
  • Earthing, RCCB rating, short-circuit capacity and motor starting are not checked. Those are the electrician's job.