T84 Calculator
You do not always need a full graphing emulator to find 25% of 200. The T84 Calculator is a stripped-down quick-calc that runs the seven operations people reach a TI-84 for most often: find a percent of a number, increase or decrease by a percent, square, square root, base-10 logarithm, and e raised to x. No keypad to learn, no emulator to load: type your numbers, pick an operation, and the answer appears to four decimal places.
This is an independent tool inspired by the TI-84’s most-used math functions. It is not affiliated with, endorsed by, or connected to Texas Instruments. If you need graphs, tables, matrices, or statistics, use our TI-84 simulator instead: that page runs the full keypad experience, while this one answers the quick questions in seconds.
Results stay hidden until you press Calculate. Independent quick-calc inspired by the TI-84; not affiliated with Texas Instruments.
Quick Answer
25% of 200 is 50, and the calculator prints Result: 50.0000. The percent operation multiplies the two values and divides by 100, so (200 × 25) ÷ 100 = 50. Increase-by-% adds that slice back on top (100 increased by 10% is 110.0000); decrease-by-% takes it off (100 decreased by 15% is 85.0000). The single-value operations ignore the second field entirely: square of 12 is 144.0000, square root of 2 is 1.4142, log base 10 of 1,000 is 3.0000, and e^1 is 2.7183.
Key takeaways
- Seven operations, one click each: percent-of, increase-by-%, decrease-by-%, square, square root, base-10 log, e^x.
- Only the three percent operations read the second value; the other four use the input value alone.
- Every answer prints to four decimal places, exactly like the tool reports.
- This page is the fast path. Graphing, tables, statistics, and matrices live on our TI-84 simulator, linked above.
- Independent quick-calc inspired by the TI-84; not affiliated with or endorsed by Texas Instruments.
How to use the T84 calculator
Type your main number, choose one of the seven operations, add the second number only for percent operations, then press Calculate. That is the entire workflow.
- Enter the input value. This is the base amount for percent operations (the 200 in “25% of 200”) or the only number for square, square root, log, and exponential.
- Pick the operation. Percentage finds X% of a number; Increase by % and Decrease by % adjust the base up or down by that slice; the other four are single-value functions.
- Enter the second value if the operation needs one. For percent work this is the percent itself (25, not 0.25). Leave it blank for square, square root, log, and e^x: they never read it.
- Press Calculate. The result box appears with the answer to four decimals. Copy or Share sends the exact result string wherever you need it.
What each operation computes
Each of the seven operations runs one fixed formula. The table shows the formula and the exact output the tool prints, verified against the live tool.
| Operation | What it does | Formula | Example output |
|---|---|---|---|
| Percentage | Finds X% of a number | (input × second) ÷ 100 | 25% of 200 → Result: 50.0000 |
| Increase by % | Adds the percent slice to the base | input + (input × second ÷ 100) | 100 + 10% → Result: 110.0000 |
| Decrease by % | Subtracts the percent slice from the base | input − (input × second ÷ 100) | 100 − 15% → Result: 85.0000 |
| Square | Multiplies the input by itself | input × input | 12² → Result: 144.0000 |
| Square root | The number that squared gives the input | √input | √2 → Result: 1.4142 |
| Log (base 10) | The power of 10 that equals the input | log₁₀(input) | log(1000) → Result: 3.0000 |
| Exponential | Euler’s number raised to the input | e^input | e^1 → Result: 2.7183 |
Percent math follows the standard definition: percent literally means per hundred, so finding X% of a number is always X ÷ 100 times that number, a point the Mathematics LibreTexts percents lesson walks through with worked examples. For deeper percent work, such as what a percent change means for a price over time, see our percentage change in price calculator; for powers beyond squaring, the exponent calculator and natural log calculator extend the log/exp pair.
T84 quick-calc vs the full TI-84 simulator
Three different tools answer three different needs. Pick the lightest one that covers your question.
This page: T84 quick-calc
Seven one-click operations. No keypad to learn, no emulator to load, answers in seconds. Best for: a percent, a root, a log, a quick e^x.
Our TI-84 simulator
Full keypad experience with graphing, tables, and statistics. Best for: plotting functions, running stats, practicing the real button layout before an exam.
Heavy emulators (ticalc84-style)
Pixel-faithful TI-84 Plus CE replicas with programming support. Best for: TI-BASIC practice and exact hardware muscle memory. Heaviest load, steepest learning curve.
The honest trade-off: this page is deliberately shallow. It cannot graph, it cannot run statistics, and it cannot replace a real TI-84 on exam day. What it does, it does faster than any emulator: one dropdown, one click, one answer. That is its entire pitch, and it is the reason the page exists alongside the simulator rather than competing with it.
Reading the results: decimals, NaN, and Infinity
Every answer prints to four decimal places. A few inputs produce special outputs, and they all mean something specific.
- NaN (not a number): the square root of a negative number, or any percent operation run with the second value left blank. The math has no real answer, and the tool says so instead of inventing one.
- -Infinity: log of 0. The power of 10 needed to reach zero does not exist in the finite sense, so JavaScript reports negative infinity.
- Infinity: e^1000 overflows what the number format can hold.
- “Please enter a valid number.”: the input field is empty or not numeric. The tool checks this before running any operation, so a typo never produces a silent wrong answer.
What the real TI-84 does that this tool skips
The physical TI-84 Plus CE is a full graphing platform: color function graphing, matrices, list-based statistics with regression models, a numeric equation solver, a finance solver, and TI-BASIC programming, as Texas Instruments documents on the official TI-84 Plus CE product page. This quick-calc implements none of that. It covers the seven scalar operations because those are the ones students and shoppers reach for between classes.
One caution for students: an online tool is not an exam tool. The College Board’s SAT calculator policy permits graphing calculators without CAS features but bans phones, tablets, and any device with wireless or camera capability, so practice on this page but bring an approved handheld to test day.
Frequently asked questions
It runs seven one-click math operations: find X% of a number, increase by %, decrease by %, square, square root, base-10 logarithm, and e raised to x. Type a number, pick an operation, press Calculate, and the answer prints to four decimal places. It is the fast path for quick answers, not a graphing emulator.
Choose the Percentage operation, type the base number in the input field, and type the percent in the second field (25, not 0.25). The tool multiplies the two values and divides by 100: 25% of 200 is (200 × 25) ÷ 100 = 50, printed as Result: 50.0000.
Percentage answers “what is the slice”: 25% of 200 is 50.0000. Increase by % answers “what is the base plus the slice”: 100 increased by 10% is 110.0000. Decrease by % answers “what is the base minus the slice”: 100 decreased by 15% is 85.0000. Pick the one that matches the question you are actually asking.
No. This is an independent tool inspired by the TI-84’s most-used math functions. It is not affiliated with, endorsed by, or connected to Texas Instruments. For the official hardware, see Texas Instruments’ TI-84 Plus CE product page linked in the references below.
NaN appears when the math has no real answer, such as the square root of a negative number, or when a percent operation runs with the second value blank. Infinity appears when a result overflows the number format, like e^1000, and log of 0 reports -Infinity. An empty or non-numeric input shows “Please enter a valid number.” instead of guessing.
Whenever the question involves graphs, tables, matrices, statistics, or programming, use our TI-84 simulator page, which recreates the full keypad experience. Keep this quick-calc for the scalar questions: a percent, a root, a log, or an exponential, answered in seconds with no emulator to load.
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References
- Texas Instruments. TI-84 Plus CE Graphing Calculator (official product page: full-color graphing, rechargeable battery, exam approvals for PSAT, ACT, SAT, IB, and AP). Accessed October 24, 2026.
- College Board. SAT Suite of Assessments Calculator Policy (non-CAS graphing, scientific, and 4-function calculators allowed; phones, tablets, wireless, and camera devices prohibited). Accessed October 24, 2026.
- Mathematics LibreTexts (Rio Hondo College). 1.5: Percents (percent as parts per hundred; part = percent × whole). Accessed October 24, 2026.
- Lumen Learning. Quantitative Reasoning: Percent (the percent equation: Percent × Base = Amount). Accessed October 24, 2026.
- BCcampus Open Textbooks. Adult Literacy Fundamental Mathematics: Finding a Percent of a Number (increases and decreases as percent-of-a-number problems). Accessed October 24, 2026.