Start with the slides for the quick version, then go deeper with the full study notes.
Short Study Notes in the form of Slides
Read the notes first. If the method in a worked example clicks, you're ready for the questions.
Short Study Notes — Standard Form
Start with these resources to cover the key concepts, then work through the practice questions.
Page 1 / 0
Detailed Notes
Full prose, callouts and a recap — built for A* mastery, not just a quick scan.
Take these study notes with you
Download a branded PDF — full prose, callouts, recap and memorise list for Standard Form, ready to print or save offline.
Standard Form — Cambridge IGCSE 0580 Maths Extended (2026)
Write very large and very small numbers as a×10n where 1≤a<10 and n is an integer. The form is non-negotiable; calculator skills and index laws do the rest.
What you’ll learn
Mapped to the Cambridge IGCSE 0580 syllabus (2025-2027).
E1.4 — Use the standard form a×10n where n is an integer and 1≤a<10.
Convert between standard form and ordinary form.
Calculate with numbers in standard form, including addition, subtraction, multiplication, and division.
What standard form looks like
a×10n with a between 1 (inclusive) and 10 (exclusive). One non-zero digit before the decimal point.
Standard form writes any positive number as a×10n where 1≤a<10 and n is an integer.
The constraint 1≤a<10 is what makes it "standard". 20×104 is a correct numerical value but NOT standard form — convert to 2×105.
Examples in standard form.
Ordinary
Standard form
4,500
4.5×103
3,200,000
3.2×106
0.000072
7.2×10−5
0.6
6×10−1
Conversion procedure.
Big number → standard form. Move the decimal point LEFT until exactly one non-zero digit is in front. Count the moves — that's n, positive.
Small number → standard form. Move the decimal point RIGHT until exactly one non-zero digit is in front. Count the moves — that's n, negative.
Reverse direction (standard → ordinary). Move the decimal point right by n (if positive) or left by ∣n∣ (if negative).
Count the decimal-point moves to get n — left moves give a positive exponent, right moves a negative one.
Form: a×10n with 1≤a<10.
Big numbers: positive n.
Small numbers (less than 1): negative n.
Count decimal moves to find n.
Multiplying and dividing in standard form
Multiply the a values, then handle the powers of 10 with index laws.
Multiplication.(a×10m)×(b×10n)=(ab)×10m+n.
If ab is no longer between 1 and 10, ADJUST: shift one decimal and bump the exponent.
Worked.(3×104)×(2.5×106)=7.5×1010.
Worked needing adjustment.(4×105)×(5×103)=20×108=2×109.
Division.b×10na×10m=ba×10m−n.
Worked.2×1048×1012=4×108.
Worked needing adjustment.6×1023×106=0.5×104=5×103.
Handle the a-values with ordinary arithmetic and the powers of 10 with index laws — then adjust if a leaves [1, 10).
Powers and roots in standard form.
(a×10n)k=ak×10nk.
a×10n — adjust n to even and use a×10n=a×10n/2.
Worked.4×106=2×103.
Worked.2.5×105 — odd exponent, rewrite as 25×104, then 25×102=5×102.
Multiply: (a⋅b)×10m+n.
Divide: (a/b)×10m−n.
Adjust if a falls outside [1,10).
For square roots, force the exponent to be even first.
Adding and subtracting in standard form
You can't add directly unless the powers of 10 match. Convert to a common power, then add.
Adding/subtracting numbers in different powers of 10 requires writing them with the SAME power first.
Worked.5.2×104+3.1×103.
Make both have ×104:
3.1×103=0.31×104.
Sum: (5.2+0.31)×104=5.51×104.
Worked.4.8×10−3−2×10−4.
Make both have ×10−3:
2×10−4=0.2×10−3.
Difference: (4.8−0.2)×10−3=4.6×10−3.
Tip. Choose the LARGER power of 10 as the common one — that's the one most likely to leave the answer in standard form without further adjustment.
Same power of 10 first, then add/subtract.
Choose the larger exponent as the common one.
Adjust at the end if a∈[1,10).
Standard form on a calculator
Use the dedicated key. Typing '× 10 ^ n' by hand multiplies by 10 first and then raises — wrong order.
Casio classpad / fx calculators have a dedicated key for entering ×10n. It's labelled EXP, EE, ×10x, or similar.
To enter 3.2×106: type 3.2 → EXP → 6. (NOT 3.2 × 10 ^ 6 — that does the right thing for this case but goes wrong for negative exponents because of operator precedence.)
To enter 4.7×10−5: type 4.7 → EXP → (-5).
Calculator displays usually show 3.2×106 as 3.2$\boxed{06}$ or 3.2E6. Always rewrite the result back to proper standard form on your answer line — examiners deduct marks for 3.2E6 written down.
Use the EXP / ×10x key — don't type by hand.
Wrap negative exponents in brackets.
Calculator's E notation is NOT standard form.
Rewrite as a×10n on the answer line.
How it’s examined
Standard-form questions are guaranteed on every paper. Paper 2 typically asks to convert to/from standard form (1 mark) and to calculate (a×10m)×(b×10n) in standard form (2 marks). Paper 4 hides standard form inside science contexts (mass of atoms, distance to stars). Examiner reports flag two recurring slips: leaving the answer in non-standard form like 20×106, and writing the calculator's E notation on the answer line.
Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.
Take this whole topic with you
Download a branded revision sheet — worked examples, formulae, definitions and common mistakes for Standard Form, ready to print or save as PDF.
Step-by-step worked examples — Standard Form
Step-by-step solutions to past-paper-style questions on standard form, written exactly the way a tutor would explain them at the board.
1Convert ordinary numbers to standard form
Core• conversion
▼
Question
Write in standard form: (a) 4,530,000, (b) 0.000082, (c) 73.
Step-by-step solution
Step 1
(a) Move the point so 4.53 is between 1 and 10: 6 places left → 4.53×106.
Step 2
(b) 8.2 is between 1 and 10: 5 places right → 8.2×10−5.
Step 3
(c) 7.3 between 1 and 10: 1 place left → 7.3×101.
Answer
(a) 4.53×106 (b) 8.2×10−5 (c) 7.3×101
2Convert standard form back to ordinary
Core• conversion
▼
Question
Write as ordinary numbers: (a) 6.04×104, (b) 1.27×10−3.
Step-by-step solution
Step 1
(a) Move 6.04 four places right → 60,400.
Step 2
(b) Move 1.27 three places left → 0.00127.
Answer
(a) 60,400 (b) 0.00127
3Multiply numbers in standard form
Extended• Adapted from 0580/42 Oct/Nov 2023 Q11• multiplication
▼
Question
Calculate (3.5×106)×(4×10−2) in standard form.
Step-by-step solution
Step 1
Multiply the coefficients and add the indices.
(3.5×4)×106+(−2)=14×104
Step 2
Adjust so coefficient is between 1 and 10.
14×104=1.4×105
Answer
1.4×105
Examiner tip
An answer of 14×104 is not in standard form. Always check that 1≤a<10.
4Add numbers in standard form
Extended• addition
▼
Question
Calculate (2.3×105)+(4.1×104) in standard form.
Step-by-step solution
Step 1
Equalise indices: 4.1×104=0.41×105.
Step 2
Add: 2.3+0.41=2.71.
Step 3
Result: 2.71×105.
Answer
2.71×105
5Divide numbers in standard form
Extended• Adapted from 0580/22 May/Jun 2024 Q15• division
▼
Question
Calculate 1.5×1036.0×108, giving your answer in standard form.
Step-by-step solution
Step 1
Divide the coefficients and subtract the indices.
1.56.0×108−3=4×105
Step 2
Coefficient 4 satisfies 1≤4<10, so the answer is already in standard form.
Answer
4×105
Examiner tip
The 2024 mark scheme awards a method mark for showing the subtraction of indices (108−3). Candidates who jump straight to the final number lose the method mark even when the answer is correct.
6Subtract numbers in standard form with different indices
Extended• Adapted from 0580/42 Oct/Nov 2022 Q5• subtraction
▼
Question
Calculate (5.6×106)−(8.4×105), giving your answer in standard form.
Step-by-step solution
Step 1
Equalise indices to 106: 8.4×105=0.84×106.
Step 2
Subtract: 5.6−0.84=4.76.
(5.6−0.84)×106=4.76×106
Answer
4.76×106
Examiner tip
The examiner report flags that candidates often subtract the coefficients without equalising the powers, producing nonsense like −2.8×10?. Always rewrite both numbers to share the same power of 10 first.
7Apply standard form to a population context
Extended• Adapted from 0580/42 May/Jun 2023 Q4• applied, context
▼
Question
The population of a country is 4.8×107. The total land area is 3.2×105km2. Find the population density (people per km²), giving your answer in standard form.
Step-by-step solution
Step 1
Population density =areapopulation.
3.2×1054.8×107
Step 2
Compute coefficient ratio and index difference.
=3.24.8×107−5=1.5×102
Step 3
Coefficient 1.5 is in range, so the answer is in standard form: 1.5×102 people per km².
Answer
1.5×102people/km2 (i.e. 150 people/km²)
Examiner tip
Examiners reward candidates who explicitly state the formula "population density = population ÷ area" before substituting. The 2023 mark scheme awarded a method mark for the formula even when the arithmetic was wrong.
8Order three numbers given in standard form
Extended• Adapted from 0580/22 Feb/Mar 2024 Q8• ordering, comparison
▼
Question
Place these numbers in ascending order: A=3.6×10−4, B=9.1×10−5, C=4.0×10−4.
Step-by-step solution
Step 1
Equalise the powers. Rewrite B=9.1×10−5=0.91×10−4.
Step 2
Now compare the coefficients with the same power: 0.91,3.6,4.0.
Step 3
Ascending: 0.91<3.6<4.0, which gives B<A<C.
Answer
B<A<C (i.e. 9.1×10−5<3.6×10−4<4.0×10−4).
Examiner tip
The examiner report flags that candidates routinely treat a larger coefficient as a larger number — ignoring the power. Always equalise powers first; then compare coefficients.
9Square a number in standard form
Extended• powers
▼
Question
Calculate (2.5×10−3)2, giving your answer in standard form.
Step-by-step solution
Step 1
Square the coefficient and double the index.
(2.5)2×102×(−3)=6.25×10−6
Step 2
Coefficient 6.25 is in range — answer is in standard form.
Answer
6.25×10−6
Examiner tip
Examiners reward candidates who write the index law (×10k)n=×10kn explicitly. Doubling the index (rather than squaring it: 10(−3)2=109) is a recurring error flagged in examiner reports.
10How many atoms? (Stretch context)
Challenge• Adapted from 0580/42 Oct/Nov 2023 Q15• context, stretch, applied
▼
Question
The mass of one carbon atom is approximately 2.0×10−23g. A diamond has mass 0.4g. Estimate the number of carbon atoms in the diamond, giving your answer in standard form to 2 significant figures.
Step-by-step solution
Step 1
Number of atoms =mass per atomtotal mass.
N=2.0×10−230.4
Step 2
Rewrite 0.4=4×10−1 to make the division easy.
N=2.0×10−234×10−1=2×10−1−(−23)=2×1022
Step 3
Answer is already in standard form to 2 s.f.
Answer
2.0×1022 atoms
Examiner tip
The 2023 mark scheme awards a stretch mark for the sign-handling on 10−1−(−23)=1022. Double-subtraction errors (writing 10−24) are flagged as the top mistake in the examiner report.
11Order-of-magnitude ratio between two physical quantities
Challenge• Adapted from 0580/42 May/Jun 2024 Q15• ratio, stretch, applied
▼
Question
The distance from the Earth to the Sun is 1.5×108km. The distance from the Earth to the Moon is 3.84×105km. How many times further is the Sun than the Moon? Give your answer in standard form to 3 significant figures.
Step-by-step solution
Step 1
Ratio =distance to Moondistance to Sun.
3.84×1051.5×108
Step 2
Divide coefficients and subtract indices.
=3.841.5×108−5=0.390625×103
Step 3
Normalise: 0.390625×103=3.90625×102.
Step 4
Round to 3 s.f.: 3.91×102.
Answer
3.91×102 (the Sun is about 391 times further than the Moon)
Examiner tip
The 2024 examiner report flags that candidates often skip the standard-form normalisation, leaving the answer as 0.391×103. That form loses the final accuracy mark even though the value is correct — the coefficient must satisfy 1≤a<10.
Key Formulae — Standard Form
The formulae you need to memorise for standard form on the Cambridge IGCSE 0580 paper, with every variable defined in plain English and a note on when to use it.
Standard form definition
n=a×10k,1≤a<10,k∈Z
a
coefficient between 1 (inclusive) and 10 (exclusive)
k
integer power of 10
When to use
Always when expressing a number in standard form.
Multiplication rule
(a×10m)×(b×10n)=(ab)×10m+n
When to use
Multiplying two numbers in standard form. Adjust coefficient afterwards.
Division rule
b×10na×10m=ba×10m−n
When to use
Dividing two numbers in standard form.
Key Definitions and Keywords — Standard Form
Definitions to memorise and the exact keywords mark schemes credit for standard form answers — sharpened from recent examiner reports for the 2026 0580 sitting.
Standard form (scientific notation)
Examiner keyword
A number written as a×10k where 1≤a<10 and k is an integer.
Coefficient
The number a in a×10k.
Index (exponent / power)
Examiner keyword
The integer k that determines the size scale.
Common Mistakes and Misconceptions — Standard Form
The traps other students keep falling into on standard form questions — taken from recent Cambridge IGCSE 0580 examiner reports and mark schemes — and how to avoid them.
✕Leaving the coefficient outside [1,10)
0580/42 — every recent series
▼
Why it happens
After multiplying, students get e.g. 14×104 and stop without normalising.
How to avoid it
Always check 1≤a<10. Adjust by moving the decimal and changing the power.
✕Adding standard-form numbers without equalising the indices
▼
Why it happens
Students mechanically add coefficients, ignoring that the powers differ.
How to avoid it
Match the powers first, then add coefficients.
✕Confusing the direction of the decimal shift for negative exponents
▼
Why it happens
Negative powers of 10 make small numbers, but students still shift left.
How to avoid it
Negative exponent → small number → shift the decimal left (more zeros).
✕Misreading calculator output (e.g. 4.5E−3) as 4.5−3
▼
Why it happens
The E or ×10 symbol is small on calculator screens.
How to avoid it
Calculator 4.5E−3 means 4.5×10−3, not 4.5 to the power −3.
Practice questions
Exam-style questions with step-by-step worked solutions. Try one before checking the method.
Past paper style quiz
Get a report showing which sub-topics you've nailed and which ones still need work.
4. Exam Quiz
Assess your understanding
Attempt a past paper style quiz for this sub-topic and get instant feedback to identify your strengths and weaknesses.
Instant AI marking SchemeExaminer's feedbackAI Detailed report
Video lesson
Short walkthrough of the concepts students most often get stuck on.
Standard Form — frequently asked questions
The things students keep getting wrong in this sub-topic, answered.