Physics is built on precise measurements, making Units and Measurements one of the most fundamental topics in the NEET syllabus. Whether you're calculating forces, energy, or even the speed of light, accurate measurements are crucial.
Understand this chapter not only helps you solve numerical problems efficiently but also lays the foundation for error-free calculations in Physics.
Building strong fundamentals in topics like Units and Measurements is key, especially if you are preparing for NEET 2026 without coaching. A self-study approach demands conceptual clarity in such foundation chapters.
This blog will provide a general overview of NEET Units and Measurements while taking a deep dive into some topics that students often find challenging.
Let’s get into the basics first.
What is a Physical Quantity?
A property of a material or system that can be quantified by measurement is a physical quantity. Examples include length, velocity, time, mass, force, and more.
However, attributes like beauty, intelligence, handsomeness, emotions, or happiness are subjective and cannot be measured quantitatively, so naturally, they are not considered physical quantities.
Physics is an experimental science, and experiments rely on measuring various physical quantities through which the laws of Physics are expressed. Without measurement, scientists would be unable to communicate their findings effectively or compare experimental results across different laboratories.
To express a physical quantity, we need to select a unit and then find out how many times that unit is contained in the given physical quantity.
Physical Quantity (Q) = Magnitude × Unit
= n × u
n= numerical value, u= unit
A Unit of measurement is a reference standard used to express a physical quantity in multiples of that standard.
A measurement is expressed as a numerical value plus the appropriate unit.
Example: metre, newton, second, kilogram, joule, watt etc.
These units can be further divided into two main categories. Let’s move on to the classification.
Fundamental Units and Derived Units
- Fundamental Units: The units assigned to fundamental (or base) quantities are called fundamental units. These cannot be derived nor resolved into any other units. (e.g., kilogram, metre, second, etc.)
- Derived Units: All other physical quantities that can be expressed as combinations of these fundamental units, known as derived units. (e.g., velocity, acceleration, force, etc.)
- Practical Units: In real-world applications, we often use practical units that are easier to work with. These units are neither fundamental units nor derived units. (e.g., centimetre, celsius, minute, hour, etc.)
System of Units
The complete collection of both fundamental and derived units is referred to as a system of units.
Some of the most common systems of units are:
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CGS System
It is also called as Gaussian system of units. Simply put, in the CGS system, distances are measured in centimetres, weights in grams, and time in seconds.
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MKS System
Moving on to the MKS system, which is also known as the Giorgi system. In simple terms, the MKS system measures distances in metres, weights in kilograms, and time in seconds.
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FPS System
Also known as the British Engineering system, foot, pound, and second are used for measurements of length, mass, and time.
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S.I. System
This is called the International System of Units (S.I.)—the most widely used measurement system in the world. It includes seven fundamental quantities, each with its own standard unit. These units help ensure consistency in scientific measurements everywhere.
| Sr. No. | Quantity | Unit | Symbol |
| 1 | Length | Metre | m |
| 2 | Mass | Kilogram | kg |
| 3 | Time | Second | s |
| 4 | Electric Current | Ampere | A |
| 5 | Temperature | Kelvin | K |
| 6 | Amount of Substance | Mole | mol |
| 7 | Luminous Intensity | Candela | cd |
Least Count of Measuring Instruments
With a solid grasp of the System of Units, we can then examine how the Least Count of Measuring Instruments affects our ability to obtain precise measurements.
Imagine you are an engineer designing a new smartphone. You need to measure the thickness of the phone's glass screen so it fits perfectly into the frame.
You start with a ruler – It has millimetre (mm) markings, so you measure the glass and find it’s about 1 mm thick. But is it 1.1 mm or 0.9 mm? You can’t tell for sure.
You switch to a vernier caliper with a least count of 0.01 cm (or 0.1 mm). Now you can see the exact thickness, like 1.02 mm or 0.98 mm. Much better.
For better precision, you use a screw gauge. It has a least count of 0.01 mm, allowing you to measure 1.007 mm. Now your measurements are extremely precise, ensuring the screen fits perfectly into the frame of the phone.
In industries like electronics, aviation, and medicine, even a tiny measurement error can cause huge problems. That’s why engineers and scientists use instruments with very small least counts to ensure accuracy and perfection.
Errors in Measurement
No measurement is perfect, there is always some level of inaccuracy. Error is the amount by which a measured value differs from the actual value.
Types of Errors
- Systematic Errors: Occur due to faults in instruments, incorrect methods, or personal errors. They can be minimised but not entirely eliminated.
- Random Errors: Arise due to unpredictable fluctuations in measurements. These errors can be corrected by taking multiple readings and averaging them.
- Least Count Errors: These are the errors associated with the resolution of the instrument.
- Absolute Errors: It is how much your measurement differs from the actual value. It tells you how far off your measurement is.
Order of Magnitude
In the topic of Units and Measurements, Order of Magnitude is a quick way to compare sizes of numbers using powers of 10. It helps us understand how big or small a number is without focusing on exact values.
For example:
- The Earth’s radius is 6,371 km, which is close to 107 km. So, its order of magnitude is 107.
- The thickness of a human hair is about 0.0001 m, which is close to 10⁻⁴ m. So, its order of magnitude is 10⁻⁴.
Significant Figures
When solving Physics problems in NEET, precision matters. But have you ever wondered why some numbers are written with extra decimal places while others are rounded off? That’s where significant figures from Units and Measurements chapter come in.
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What are Significant Figures?
The digits in a number that hold meaningful information regarding its precision are called significant figures. They help ensure that calculations and measurements are as accurate as possible without pretending to be more precise than our measuring tools allow.
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Why Do We Use Significant Figures?
Imagine counting candies in a jar:
If you say there are 1,234 candies, you are being very precise. If you write 1,234.0 candies, you are being extra precise by showing confidence in every digit. If you round it to 1,200 candies, you are giving an approximate count.
In Physics, we don’t always get exact numbers. Measuring tools have limits, and we need to express our answers based on the precision of those tools.
Mastering precision in Physics problems not only reduces mistakes but also plays a big role in achieving higher scores. For example, if you’re aiming for 650+ in NEET 2026, handling concepts like errors and significant figures correctly can save you crucial marks.
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Rules of Significant Figures
To use significant figures correctly, follow these basic rules:
- All nonzero digits are significant.
E.g.: The number 123 has three significant figures.
- Zeroes between nonzero digits are significant.
E.g.: The number 102 still has three significant figures.
- Leading zeroes (zeroes before the first nonzero digit) are NOT significant.
E.g.: The number 0.0056 has two significant figures (5 and 6).
- Trailing zeroes (zeroes at the end) are significant ONLY if there’s a decimal point.
E.g.: The number 343.000 has six significant figures.
Applying Significant Figures in NEET 2026 Physics
When solving numerical problems in NEET Physics, Significant Figures help you determine how to round off your answers.
When multiplying or dividing numbers with similar number of significant figures, the answer should have the same number of significant figures as the least precise number in the calculation. If you measure a length as 5.32 cm, your final answer must not have more precision than this measurement allows.
An exact number has infinite number of significant figures, for example, 5 can be written as 5.0, or 5.00, or 5.000, and so on.
Rounding Off Values
- If a digit to be dropped is less than 5, the preceding digit is left unchanged.
x= 3.62 is rounded off to 3.6.
- If a digit to be dropped is more than 5, the preceding digit is raised by one.
x= 7.59 is rounded off to 7.6.
- If a digit to be dropped is 5 or 5 followed by zeroes, then the preceding digit is left unchanged, if it is even.
x= 3.250 becomes 3.2.
- If a digit to be dropped is 5 or 5 followed by zeroes, then the preceding digit is raised by one, if it is odd.
x= 3.750 becomes 3.8.
Dimensions and Dimensional Analysis:
When studying Physics for NEET, you’ll often come across different physical quantities like speed, force, energy, and pressure. But how do we know if an equation is correct or if two quantities can be compared? That’s where Dimensions and Dimensional Analysis help.
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What are Dimensions?
In simple terms, dimensions tell us what a physical quantity is made of in terms of basic fundamental units.
The three most fundamental physical quantities are:
Length (L) → measured in meters (m)
Mass (M) → measured in kilograms (kg)
Time (T) → measured in seconds (s)
All other physical quantities are combinations of these basic ones.
For example:
Speed = Distance ÷ Time → [L] / [T] = [L T⁻¹]
Acceleration= Change in velocity ÷ Time → ([L T⁻¹]) / [T] = [L T⁻²]
Force = Mass × Acceleration → [M] × [L T⁻²] = [M L T⁻²]
Energy = Force × Distance → [M L T⁻²] × [L] = [M L² T⁻²]
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What Is Dimensional Analysis?
Think of dimensional analysis as a way to check, convert, and derive Physics formulae using units.
It is used to:
- Check the correctness of equations (Principle of Homogeneity).
- Convert units from one system to another.
- Derive new formulas.
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Principle of Homogeneity
The Principle of Homogeneity in dimensional analysis states that an equation is valid only if all its terms have the same dimensions. The magnitudes of physical quantities may be added together or subtracted from one another only if they have the same dimensions. In other words, we can add or subtract similar physical quantities.
For example, in the equation of motion:
s = ut + (1/2)at², every term has the dimension of length [L], proving the equation is correct.
However, if an equation like:
v = u + at² is given, dimensional analysis quickly reveals it as incorrect. This principle is a powerful tool in NEET Physics, helping students verify formulae, eliminate wrong answers in MCQs, and even derive new equations with confidence.
Such smart shortcuts are often part of NEET toppers’ daily study strategies, where they focus on conceptual clarity and speed.
Key Tips for NEET 2026 Units and Measurements Chapter
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Memorise SI Units and Prefixes:
Know the seven SI base units (metre, kilogram, second, ampere, kelvin, mole, candela). Understand commonly used prefixes (milli-, micro-, nano-, kilo-, mega-).
Mnemonics Made Easy: Pick Your Favourite!
Remembering all 7 SI base units: Metre, Kilogram, Second, Ampere, Kelvin, Mole, Candela can feel tricky at first. But with the right mnemonic, it’s a breeze. Here are a few fun ones to choose from:
- My Kind Sister Always Keeps Me Cheerful.
- Many Kids Study And Keep Making Calculations.
- My King’s Smart Advice Keeps Minds Clear.
Which one sticks in your head the best? Pick your favourite and let us know in the comments below!
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Master Units Conversions
Convert between different units systems (CGS, MKS, FPS, SI). Practise numerical problems on conversion of units.
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Accuracy, Precision, and Errors
Understand systematic and random errors in measurement. Learn formulas for absolute error, relative error, and percentage error.
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Significant Figures Rules
Follow the rules for addition, subtraction, multiplication, and division with significant figures. Always round off answers correctly based on significant figures.
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Instrument Least Count and Measurement
Understand the least count of instruments (vernier calipers, screw gauge, meter scale). Solve problems based on vernier caliper and screw gauge readings.
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Practise Time-bound Problem Solving
Solve NEET previous years’ questions and mock tests to improve speed and accuracy.
The chapter Units and Measurements lays the foundation for understanding physical quantities and their measurement. It emphasises the importance of accuracy, precision, and error analysis in experiments. By mastering this chapter, students gain a fundamental understanding of SI units, significant figures, and different types of errors in measurements, which are crucial for solving numerical problems in Physics.
Frequently Asked Questions about NEET Physics Units and Measurements
1. What is the significance of the Units and Measurements chapter in NEET Physics?
Ans: The Units and Measurements chapter is fundamental for NEET Physics as it builds the basic understanding of physical quantities, their measurements, and error analysis, which are essential for solving numerical problems in all Physics topics.
2. How many questions from Units and Measurements can be expected in the NEET exam?
Ans: Units and Measurements chapter is a low weightage but a crucial topic in NEET Physics. Based on previous years’ trends, 1–2 questions (approximately 2–4 marks) are typically asked in NEET. In fact, 29 questions from Units and Measurements have been asked across past NEET exams, showing that while the chapter carries relatively low weightage each year, it still holds consistent importance.
For a complete subject-wise and chapter-wise breakdown, read our NEET UG 2026 Chapter-wise Weightage Guide. Some years, there may be no direct question, but the concepts are indirectly applied in other Physics topics like kinematics, laws of motion, and thermodynamics.
3. What are the fundamental units in the International System of Units (SI)?
Ans: Length (m), mass (kg) , time (s), electric current (A), temperature (K), amount of substance (mol), and luminous intensity (cd) are the fundamental units in the S.I. system.
4. How can I effectively prepare for Units and Measurements for NEET?
Ans: Start by thoroughly understanding the SI base units, derived units, and unit conversions between different measurement systems. Focus on dimensional analysis, as it helps verify equations and derive relationships between physical quantities.
Practise error analysis, significant figures, and least count concepts, as NEET often tests precision and accuracy in measurements. Solve previous years’ NEET questions and mock tests. Prioritise conceptual clarity and numerical practice, ensuring you can apply these principles across other Physics topics.
5. What is dimensional analysis, and why is it important?
Ans: In the NEET Units and Measurements, Dimensional Analysis is a technique used to study the dimensions (fundamental units) of physical quantities to verify equations, derive formulas, and convert units. It is based on the principle of homogeneity, which states that an equation is valid only if all terms have the same dimensions.
It helps ensure the correctness of equations and calculations by verifying that the units on both sides of an equation match.
6. How do errors in measurements impact experimental results?
Ans: Errors in measurements can significantly affect experimental results by reducing their accuracy, precision, and reliability. These errors cause differences from the true value, leading to incorrect conclusions or inconsistencies in data.
7. Are there any recommended resources for practicing questions on Units and Measurements?
Ans: Yes, our 38 Years NEET Physics Previous Solved Papers (PSP) is a highly recommended resource for practising questions on the Units and Measurements chapter. It provides a collection of questions from this chapter that have appeared in the NEET exam over the past 38 years, helping students identify important patterns and frequently tested concepts.
