Online Calculators

The page loads 18 calculators grouped into five categories: Math & Statistics, Finance & Business, Date & Time, Health & Fitness, and Payment Fees. Chips filter the tile grid; clicking a tile swaps the panel underneath. Nothing navigates, so moving from a loan EMI to a Stripe fee to a percentage change costs one click each rather than three page loads and three cookie banners. Every calculator is reactive: state changes trigger a recompute on each keystroke, so there is no Calculate button to hunt for and no stale result sitting on screen after you edit an input. Each result card carries a copy button that puts that value on your clipboard exactly as displayed, currency symbol and all.

The calculator is a React client component wired to plain TypeScript functions. There is no fetch call, no API route and no server action in the calculation path — the numbers you type never leave the browser tab. That matters more here than on most tool pages, because the inputs are personal: birth dates, salary and loan principals, revenue and cost figures, body weight and age. Most fee and TDEE calculators ranking for these terms are lead-generation pages attached to a SaaS product, wrapped in analytics and ad scripts. Nothing is persisted here — no localStorage, no cookies for state — so a refresh empties every field, and switching calculators unmounts the panel and clears its inputs with it.

Every calculator on this page uses a named, checkable formula rather than an opaque black box. If you are pasting a result into a pricing model, a payroll sheet or a statistics assignment, you need to know which convention was applied — population versus sample variance, z versus t, Mifflin-St Jeor versus Harris-Benedict. Those choices are listed below and in the FAQ so you can reproduce any figure by hand or in a spreadsheet.

Three of these calculators exist because the naive version of the arithmetic is wrong in a way that compounds. Adding your processor's percentage to an invoice undercharges you: bill $102.90 to net $100 on Stripe US and you actually receive $99.62, because the fee lands on the grossed-up total — the "I Want to Receive" mode inverts it properly and returns $103.30. Treating markup as margin overstates profit on every line item: 50% markup is a 33.33% margin, and the error scales with volume. Extracting tax from a GST- or VAT-inclusive total is a division, not a subtraction, so the inclusive switch on the Sales Tax and GST calculators applies amount / (1 + rate/100) rather than knocking the percentage off the top. The CPM calculator solves in all three directions — CPM from spend and impressions, spend from CPM, impressions from budget.

Stated plainly so you do not waste a click. There is no arithmetic keypad, no scientific functions and no expression parser — this is a set of domain calculators with typed fields, not a desk calculator. Currency output is formatted as USD via Intl.NumberFormat regardless of the region you pick in the fee calculators, so read UK and EU results as numbers rather than symbols. Processor rates are the standard published ones and cannot be edited to your negotiated pricing. GST is limited to the four Indian slabs (5, 12, 18, 28%) and does not split CGST and SGST or apply cess. Calorie and TDEE take metric input only, with no imperial toggle. The hours calculator wraps one overnight boundary and ignores breaks and overtime rules.

Eighteen, in five categories. Math and Statistics: percentage, average, confidence interval, probability. Finance and Business: sales tax, margin, discount, CPM, loan/EMI, GST. Date and Time: age, days, hours, months. Health and Fitness: calorie, TDEE. Payment Fees: PayPal, Stripe. Category chips filter the tile grid and clicking a tile swaps the panel below without a page load. Every calculator recomputes on each keystroke, and each result card carries a copy button. The page opens on the Age Calculator.

Nothing leaves the page. The component is a React client component and every calculation is a pure TypeScript function running in your browser — there are no fetch calls and no API routes anywhere in the calculation path. Your birth date, salary, loan principal, weight and revenue figures are never transmitted, logged or persisted. Nothing is written to localStorage or cookies, so a refresh clears every field, and switching to a different calculator unmounts the panel and resets its inputs. No account or signup is required.

No. This page has no arithmetic keypad, no trigonometric or logarithmic functions and no expression parser — it is 18 domain calculators with typed input fields, not a desk-calculator replacement. If you need sin, log, exponents or free-form expressions, use a scientific calculator. What this page covers instead are the multi-step calculations that are tedious by hand: EMI amortization schedules, reverse fee gross-ups, tax-inclusive extraction, margin-to-markup conversion and confidence intervals.

The standard amortizing payment formula: M = P · i(1 + i)^n / ((1 + i)^n − 1), where P is principal, i is the annual rate divided by 1200, and n is the term in months. A 0% rate falls back to P / n. Enter the term in years or months using the dropdown. Clicking Show Amortization Schedule expands a scrolling table with one row per month — payment, principal, interest and closing balance — so a $100,000 loan at 5.5% over 30 years gives a payment near $568 and 360 rows.

PayPal defaults: 2.99% + $0.49 (US), 2.90% + £0.30 (UK), 2.90% + €0.35 (EU), 2.90% + $0.30 (Canada), 2.60% + $0.30 (Australia), 4.49% + $0.49 (international). Stripe defaults: 2.9% + $0.30 (US), 2.4% + £0.20 (UK), 2.5% + €0.25 (EU), 2.9% + $0.30 (Canada), 1.75% + $0.30 (Australia), 3.9% + $0.30 (international). These are standard published rates; negotiated pricing, Billing surcharges and currency-conversion fees are not modelled, and the rates are fixed constants you cannot edit.

Use the "I Want to Receive" mode in either fee calculator. It solves the inverse: charge = (target + fixed fee) / (1 − rate / 100). To net $100 on Stripe US at 2.9% + $0.30 you invoice $103.30; on PayPal US at 2.99% + $0.49 you invoice $103.59. Simply adding 2.9% and charging $102.90 nets you $99.62 — about 38 cents short — because the percentage is taken on the grossed-up total, not on your target. Results are formatted as USD whichever region you pick.

Population. The Average calculator divides the sum of squared deviations by n, not by n − 1, so it reports population variance and population standard deviation, both to four decimal places. That is correct when your numbers are the entire dataset. If they are a sample and you need Bessel's correction, multiply the reported variance by n / (n − 1) and take the square root. Mode is only listed when a value actually repeats; with all-unique values it displays None. Numbers can be separated by commas or spaces.

Fixed two-tailed z-scores, not the t-distribution: 1.282 (80%), 1.440 (85%), 1.645 (90%), 1.960 (95%), 2.576 (99%), 2.807 (99.5%) and 3.291 (99.9%). Standard error is σ / √n and margin of error is z × SE, so the interval is mean ± z · σ / √n. You supply the mean, the standard deviation and the sample size. Because it is z-based, intervals run slightly too narrow for small samples — below roughly n = 30, substitute the appropriate t-value by hand.

Mifflin-St Jeor, on metric inputs only: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 for men, and the same expression − 161 for women. BMR is multiplied by an activity factor of 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (active) or 1.9 (very active) to give TDEE. The Calorie tool then offsets TDEE by ±250, ±500 and ±1000 kcal, labelled as roughly 0.25, 0.5 and 1 kg per week. Weight must be in kilograms and height in centimetres; there is no imperial toggle.

Only the TDEE calculator shows macros — the Calorie calculator shows six weight-goal targets instead. TDEE has a goal selector: maintain uses TDEE as-is, lose subtracts 500 kcal, gain adds 500. From that target, protein is set at 2 g per kg of bodyweight, fat at 25% of target calories divided by 9, and carbohydrate takes whatever calories remain divided by 4. Grams and calories are shown for each of the three, using 4/4/9 kcal per gram.

Margin is profit as a percentage of revenue; markup is profit as a percentage of cost. The calculator reports cost, revenue, profit, margin and markup together from any of three modes: cost and revenue; cost and a target margin (revenue = cost / (1 − margin / 100)); or cost and a target markup (revenue = cost × (1 + markup / 100)). A 50% markup on $50 cost yields $75 revenue and a 33.33% margin — the gap that quietly breaks pricing spreadsheets.

Yes. It converts both times to minutes past midnight and subtracts; when the result is negative it adds 1,440 minutes, so 22:30 to 06:15 returns 7 hours 45 minutes instead of a negative span. Output is hours and minutes, total minutes, and decimal hours to two places — the last is what payroll and timesheet systems normally expect. It wraps a single midnight boundary only, and does not model spans longer than 24 hours, unpaid breaks, or overtime multipliers.