Table of Figures and Table of Tables: How to Navigate BS 7671 Fast

Ask any electrician who has just failed the 18th Edition exam what went wrong, and you will usually hear the same thing: they ran out of time. Not because they did not know the material, but because they spent forty minutes of a two-hour paper flicking back and forth through a 700-page book trying to find the right table.

 

There is a fix for this, and it has been sitting at the back of your copy of BS 7671 the whole time. Two short sections — the Table of Figures and the Table of Tables — list every named figure and every named table in the book, with the page number for each. Most candidates never open them.

 

This guide shows you what they contain, how the numbering system works, and how to use both to cut your lookup time down to seconds.

What These Two Sections Actually Are

Turn to the contents page at the front of BS 7671 and look near the bottom. You will find two entries most people skim straight past:

 

Section	What It Lists	Where to Find It
Table of Figures	Every named figure — diagrams, charts, graphs — with its number, title and page	Near the back, before the Table of Tables
Table of Tables	Every named table in the whole book, with its number, title and page	Immediately before the index

 

Easy way to find them: They sit immediately before the index. Open the book at the very back, then thumb backwards past the index and you are there. That is faster than remembering a page number — and page numbers shift with every amendment anyway.

 

The difference between the two is worth understanding. A figure conveys an idea using picture information — a drawing, a chart, a graph, a schematic of an earthing arrangement. A table gives you usable data arranged in rows and columns: values for calculations, circuit design, maintenance requirements, or comparison against test results.

 

In an exam, figures help you understand a concept. Tables give you the number the question is asking for. Both are listed strictly in the order they appear in the book, which means they follow the Part order — a figure from Part 2 appears in the list before a figure from Part 4.

 

Decoding Figure Numbers

Once you understand the numbering convention, you can often jump straight to roughly the right place in the book without consulting the list at all.

 

Take Figure 82.1 as an example:

 

Element	Meaning
fig	It is a figure — a drawing, chart or diagram
8	Part 8 of BS 7671 (Prosumer’s Low-Voltage Installations)
82	Chapter 82
.1	The first figure in that chapter

 

So Figure 82.1 is the first figure in Chapter 82 of Part 8. The list then gives you its title as printed in the book and the page it appears on.

 

Another example: Figures 709.1 and 709.2. The leading 7 tells you this is Part 7, Special Installations or Locations. 709 is the section for marinas. The .1 and .2 are simply the first and second figures in that section, and in this case both sit on the same page.

 

Key point: Some regulations reference a figure directly in the text. When a regulation in Section 709 tells you to refer to Figure 709.3, the Table of Figures gives you the page in one step instead of turning pages hunting for it.

 

Decoding Table Numbers

The Table of Tables works the same way but rewards a bit more study, because tables are what exam questions actually ask about. It helps to think of the list as three distinct blocks:

 

Block	What It Covers	Typical Examples
Block 1	Tables in the numbered Parts (1–8)	Table 41.1, Table 41.3, Table 54.7
Block 2	Tables in Appendix 4 — and there are a lot of them	Table 4Ab, Table 4D2A, Table 4D5
Block 3	Tables in other appendices — external influences, label sizes, SPDs	Appendix 5 and 16 tables

 

For the numbered Parts, the convention mirrors the regulation numbering you already know. Table 41.1 breaks down as Part 4, Chapter 41, first table in that chapter. Table 54.7 is Part 5, Chapter 54, seventh table — the minimum CPC sizing table you will reach for constantly.

 

Exam tip: If you can decode a table number on sight, you already know which Part to open at. Table 41.3 means Part 4. Table 54.7 means Part 5. That alone saves you from the panicked full-book flick that eats time in the exam hall.

 

Our guide on Ten Essential BS 7671 Tables for the 18th Edition Exam covers the specific tables worth knowing inside out.

 

Don’t Ignore the Annexes

Some chapters have annexes — a few extra pages of supporting information attached to the end of a chapter. Tables inside an annex are numbered with a leading A.

 

Take Table A44.2:

 

Element	Meaning
A	The table is in an annex, not the chapter’s main text
44	An annex to Chapter 44 (Protection Against Voltage Disturbances)
.2	The second table in that annex

 

Chapter 44 has several annexes. They cover overvoltage protection and electromagnetic disturbance material that is genuinely examinable.

 

Important: The worst thing you can do is pretend the annexes do not exist. They do, they contain useful additional information, and question setters know that most candidates skip them. Spend ten minutes flicking through the annexes to Chapter 44 so they are not a surprise on exam day.

 

The Appendix 4 Tables

Appendix 4 is where most of the calculation work happens, and it holds more tables than any other single section of the book. Two are worth finding before you do anything else.

 

Table 4Ab — Permitted Voltage Drop

This is the table that defines the limits, and it appears in exam questions constantly:

 

Circuit Type	Max Voltage Drop	At 230 V Nominal
Lighting only	3%	6.9 V
All other circuits	5%	11.5 V

 

These percentages apply to installations supplied from a public low-voltage distribution system — the National Grid supply that comes in at the front door of a house, shop or factory. That is the case for most of the questions you will face.

 

Table 4D5 — Twin and Earth

Table 4D5 carries the full title “70 °C thermoplastic insulated and sheathed flat cable with protective conductor”, which is the formal name for the twin and earth you install every day. If you work in domestic properties you will use this table more than any other.

 

Here is how it is laid out:

 

Part of the Table	What It Gives You
Left-hand column	Conductor cross-sectional area (line and neutral only — the CPC is not listed, because current-carrying capacity assumes a fault-free circuit)
Column headings	Installation reference methods with a brief description of each
Main body	Current-carrying capacity for each conductor size against each reference method
Right-hand column	Voltage drop in mV/A/m for use in calculations

 

Remember: The current-carrying capacity depends entirely on which reference method you read across to. Clipped direct, in a stud wall with insulation, and in conduit in a thermally insulating wall give very different values for the same cable. Our guide to Installation Reference Methods and Cable Sizing walks through picking the right column.

 

There is also a summary list of most Appendix 4 tables near the front of the appendix — rating factors in the top half of that page, cable data tables in the bottom half. Worth tabbing.

 

Worked Example: A Voltage Drop Question

Here is the kind of question the exam asks, and how the two tables work together to answer it.

 

The question: A 230 V, 20 A heater circuit is supplied from the public low-voltage distribution system and wired in 2.5 mm² twin and earth, clipped direct, with a circuit length of 40 m. Calculate the actual voltage drop and decide whether the cable size is acceptable.

 

The formula is:

 

Voltage drop = (mV/A/m × I_b × L) ÷ 1000

 

Gathering what we need:

 

Value	Source	Figure
mV/A/m for 2.5 mm²	Table 4D5	18
Design current Ib	Given in the question	20 A
Length L	Given in the question	40 m
Permitted maximum	Table 4Ab (5% of 230 V)	11.5 V

 

Running the numbers:

 

(18 × 20 × 40) ÷ 1000 = 14.4 V

 

14.4 V is greater than the permitted 11.5 V, so this design fails. Note that the 40 m is the one-way route length, not there and back — the mV/A/m figure already accounts for both conductors.

 

Fixing the Design

You have three variables, and only one of them is actually available to you:

 

Option	Viable?	Why
Reduce Ib	No	20 A is the heater’s demand — switch it on and it draws 20 A
Reduce the length	No	The heater has to go where it has to go. A bathroom heater in the kitchen because it is nearer the consumer unit is not a design
Reduce mV/A/m	Yes	Increase the conductor cross-sectional area

 

Go back to Table 4D5, find 4 mm² in the left-hand column, and the mV/A/m drops to 11:

 

(11 × 20 × 40) ÷ 1000 = 8.8 V

 

8.8 V is comfortably under 11.5 V, so 4 mm² is acceptable. That is the whole method — and it only works quickly if you can find Table 4D5 and Table 4Ab without hunting.

 

Exam tip: Voltage drop questions almost always follow this shape: a given load, a given length, a cable size that fails, and a correct answer that is the next size up. Practise the arithmetic until it is automatic. Three Essential Formulas for the 18th Edition Exam covers this alongside the adiabatic equation and rating factors.

 

When Tables Move or Disappear

BS 7671 is amended regularly to keep up with technical developments, and tables get renumbered, relocated or dissolved into plain text when that happens. This catches people out.

 

The classic example is thermal insulation derating. A very common exam question runs:

 

A 6 mm² cable is totally surrounded by thermal insulation for a length of 200 mm. What derating factor should be applied to the current-carrying capacity?

 

There used to be a table for this in Part 5. The Table of Tables still carries an entry for Table 52.2, but it now tells you the content has moved into Appendix 4 as item 2.6 — it is no longer a named table at all, which is precisely why candidates cannot find it.

 

The answer, from item 2.6 in Appendix 4:

 

Length Surrounded by Insulation	Derating Factor
50 mm	0.89
100 mm	0.81
200 mm	0.63
400 mm	0.50

 

Key point: The Table of Tables does not just tell you where things are — it tells you where things went. When a table has been relocated or withdrawn, the entry points you to the replacement. That redirect is worth more than the original listing.

 

This matters more than usual right now. If you are sitting City & Guilds 2382-26, you are being examined on BS 7671:2018+A4:2026, and Amendment 4 has moved content around again. Our guide to Amendment 4 to BS 7671 covers what has changed.

 

Your Tabbing Strategy

Knowing the structure is only half of it. The other half is making the book physically fast to use. Tab these:

 

Priority	What to Tab	Why
1	Table of Figures	Every figure in the book, one lookup
1	Table of Tables	Every table in the book, one lookup
2	Table 41.3	Maximum Zs for protective devices
2	Table 54.7	Minimum CPC sizes
2	Table 4Ab	Permitted voltage drop — 3% and 5%
2	Table 4D5	Twin and earth — capacity and mV/A/m
3	Tables 4D2A / 4D2B	Multicore thermoplastic cable
3	Tables 4B1, 4C1, 4C2	Ambient temperature, grouping and insulation rating factors
3	Appendix 4 item 2.6	Thermal insulation derating

 

Then do the thing almost nobody does: practise using the tabs under time pressure. Have someone call out “Table 4D5” or “maximum Zs for a 32 A Type B MCB” and time how long it takes you to put a finger on the number. Under thirty seconds is where you want to be.

 

Remember: The exam is open book, but the clock does not care. Sixty questions in 120 minutes is two minutes each, and some of those questions need two or three lookups. Navigation speed is a skill you train, not a bonus you get for owning the book.

 

The same logic applies to the front of the book. Using the Contents Page and Index to Find Answers Fast covers the other half of the navigation picture — contents and index at the front, Table of Figures and Table of Tables at the back. Between them you can reach any point in BS 7671 in one or two moves.

 

Practice and Further Study

Table navigation is a skill that only improves with repetition against real questions. Test yourself on the parts where table lookups matter most:

• Part 4 — Protection for Safety quiz
• Part 5 — Selection and Erection of Equipment quiz
• Part 6 — Inspection and Testing quiz
• Part 7 — Special Installations quiz

 

Our app includes 690+ practice questions covering all 8 parts, with explanations that reference the specific regulation and table each answer comes from — so every question you work through doubles as navigation practice. The timed mock exams use the same weighted question distribution as the real paper, which is the closest you will get to rehearsing lookup speed under genuine exam pressure.

 

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