The Built-In Unit Converter — A Tour for Exam-Style Conversions
Every quantity in a Class 9–12 science or maths paper eventually needs to change its units — millilitres to litres, degrees to radians, mmHg to kPa — and typing the wrong conversion factor from memory is one of the most common, entirely avoidable ways to lose marks on an otherwise correct method. The calculator suite has a single button for this, but it opens onto a picker of 23 categories rather than one converter, and the seconds spent hunting for the right icon in an exam-prep session are seconds you would rather spend on the actual problem. This article is a tour of that picker: what each category actually converts, and four worked conversions — in pressure, angle, volume and area — using categories that do not already have their own dedicated guide on this site. For the underlying method that makes any of these conversions provable by hand rather than just trusted, see the dimensional analysis guide linked at the end; this article is about knowing which button to press.
The one relationship behind every conversion
That ratio is what the converter computes for you the instant you pick a category and type a number — it has simply memorised every conversion factor so you do not have to carry all of them into an exam. What it cannot do is choose the right category for you, and choosing wrong (for example, trying to force a temperature change through a plain multiplicative converter) is the one mistake that produces a confidently wrong answer instead of an obviously wrong one.
What the 23 categories actually cover
Opening ?view=convert shows every category as its own icon; tapping one opens
that specific converter, and the picker itself never changes the page URL further, so this
single link is the correct, honest destination for a question in any of these categories.
| Category | What it converts | Where it matters in exams |
|---|---|---|
| Length | m, cm, km, inch, mile | Mensuration, kinematics, distances in word problems |
| Mass | kg, g, mg, tonne | Sample masses in chemistry, everyday-maths problems |
| Area | cm², m², hectare | Mensuration, land/plot word problems — worked below |
| Volume | mL, L, m³, cm³ | Solution volumes, mensuration — worked below |
| Time | seconds, minutes, hours, days | Kinematics and rate-of-work problems |
| Speed | km/h, m/s | Kinematics numericals |
| Pressure | atm, mmHg, kPa | Gas-law numericals — worked below |
| Angle | degrees, radians | Trigonometry — worked below |
| Temperature | °C, °F, K | The one category that is not a simple multiplication — see the mistake box |
| Energy | J, cal, kWh, eV | Thermochemistry; see the dimensional analysis guide's own worked example |
| Power | W, kW, HP | Physics numericals |
| Density | g/cm³, kg/m³ | See the dimensional analysis guide's own worked example |
| Amount | mol ↔ mmol only | Not a mole-to-particle-count tool — a common false expectation, see below |
| Data | KB, MB, GB | Computer Applications numericals |
| Numeral system | binary, decimal, hexadecimal | See the dedicated number-systems guide on this blog |
| Currency | INR and other currencies | General-awareness and economics-linked questions |
| Finance | Nominal vs effective rate work | Commerce/applied-maths compound-interest topics |
| Discount | Percentage and successive discounts | See the dedicated discount guide on this blog |
| GST | Inclusive vs exclusive pricing | See the dedicated GST guide on this blog |
| BMI | Height/weight into a BMI value | See the dedicated BMI guide on this blog |
| Torque | N·m and related units | Rotational-mechanics numericals |
| Fuel Economy | km/L, L/100 km | Everyday-maths word problems |
Worked example 1 — Pressure
Question: A gas-law numerical states P = 740 mmHg. Express it in atm and kPa so it can be used with R = 0.0821 L atm mol⁻¹ K⁻¹.
1 atm = 760 mmHg = 101.325 kPa.
In atm: 740 ÷ 760 = 0.9737 atm
In kPa: 740 × (101.325 ÷ 760) = 740 × 0.133322 = 98.66 kPa
Both figures describe the same pressure — the converter simply saves you from carrying 760 and 101.325 into every gas-law question.
Worked example 2 — Angle
Question: A trigonometry problem gives an angle of 135° but the formula you need takes radians. Convert both ways.
135° × (π ÷ 180) = 0.75π = 2.3562 rad
Reverse check: 2.3562 × (180 ÷ π) = 2.3562 × 57.2958 = 135.0° ✓
A second, independent value: 2 rad in degrees = 2 × (180 ÷ π) = 360 ÷ π = 114.59°.
Worked example 3 — Volume
Question: A titration uses 2.5 L of a stock solution. Express this in cm³ and in m³.
1 L = 1000 cm³ = 10⁻³ m³.
2.5 L = 2.5 × 1000 = 2500 cm³
2.5 L = 2.5 × 10⁻³ = 0.0025 m³
Worked example 4 — Area
Question: A mensuration problem measures a surface as 450 cm². Convert to m² so it can be combined with a length measured in metres.
1 m² = (100 cm)² = 10,000 cm², so the factor is squared, not merely multiplied by 100.
450 ÷ 10,000 = 0.045 m²
Common mistakes with the converter itself
- Treating Temperature like every other category. °C → K is an addition of 273.15, and °C → °F is an affine map (F = C × 9/5 + 32), not a multiplication — the converter handles this correctly, but a student solving by hand who forgets it will multiply where they should have added.
- Expecting "Amount" to convert moles to number of particles. It only converts mol ↔ mmol, a plain SI-prefix step. There is no Avogadro's-number tool in the suite; that conversion (N = n × Nₐ) must be done by hand or on the Scientific Calculator.
- Forgetting a squared or cubed unit needs the factor squared or cubed too — exactly the Area example above; 1 m² is 10,000 cm², not 100.
- Reading the answer off the wrong direction. If the value you get looks absurdly large or small, you have likely typed into the "to" box instead of the "from" box and read off the reciprocal of the intended conversion.
- Assuming a category is missing before checking the full picker. With 23 categories, most school and competitive-exam conversions are already covered; scroll the picker before reaching for a hand calculation.
Where this matters across exams
| Context | Categories used most |
|---|---|
| CBSE/ICSE Class 9–10 mensuration | Area, Volume, Length |
| Class 11–12 physics practicals and numericals | Pressure, Speed, Power, Temperature |
| Trigonometry chapters | Angle |
| Computer Applications | Data, Numeral system |
| Commerce/CUET/competitive quantitative sections | Currency, Finance, GST, Discount |
Open the picker and try your own numbers. The converter covers all 23 categories above in one place, so a question in any of them is one tap away rather than a remembered factor.
Open the Unit Converter →