🧮Calculators

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5-Card Poker Hand Evaluator

Type five cards such as AS,KS,QS,JS,TS with ranks 2-9,T,J,Q,K,A and suits S,H,D,C to get the ranking, from royal flush down to high card.

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Birthday Paradox Probability Calculator

Returns the probability that at least two people in a group of n share a birthday, under the 365-day model with uniform dates and no leap years.

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Bayes Theorem Calculator

Enter the prior P(A), the hit rate P(B|A) and the false alarm rate P(B|not A) to get the posterior P(A|B) as a decimal between 0 and 1.

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Markov Chain Steady State (2 States)

Enter a = P(1 to 2) and b = P(2 to 1) for a two-state chain and get the stationary vector: pi1 = b/(a+b) and pi2 = a/(a+b).

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Expected Value of a Discrete Random Variable

Takes comma-separated values and probabilities, checks that both lists match in length and sum to 1, then returns E[X] as the probability-weighted mean.

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Binomial Probability P(X = k)

Enter trials n, successes k and success probability p to get P(X=k) = C(n,k)·p^k·(1−p)^(n−k) for a binomial random variable.

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Poisson P(X=k)

Enter the mean rate λ and a count k to get the exact Poisson probability P(X=k) = λᵏ·e⁻λ / k!, the chance of k events inside one fixed interval.

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Geometric Distribution P(X = k) Calculator

Enter a success probability p and a trial number k to get (1 - p)^(k-1) · p, the chance that the first success falls exactly on trial k.

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Hypergeometric Distribution P(X = k)

Probability of exactly k successes in a sample of n drawn without replacement from N items holding K successes: C(K,k)·C(N−K,n−k) / C(N,n).

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Conditional Probability Calculator

Works out P(A|B) by dividing the joint probability P(A∩B) by P(B), the rule behind Bayes theorem and behind any update made after new evidence arrives.

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Monty Hall: Switch vs Stay

Set the number of doors and compare your odds of winning by keeping the first pick against switching, after the host opens one losing door.

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Loan Payment (PMT) Calculator

Calculate the fixed loan payment (PMT) using the amortization formula from the amount, interest rate and term. Plan loans and mortgage installments.

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SAC Amortization Schedule: First N Payments

Enter loan amount, monthly rate and term to print the first N rows of a constant-amortization (SAC) schedule: principal, interest, payment and balance.

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Early Loan Payoff Savings Calculator

Enter amount, monthly rate, term and payoff month of a fixed-installment (Price) loan to get the balance owed, the total still due and the interest saved.

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Refinance Break-Even Point Calculator

Closing cost divided by the drop from the old to the new installment gives the months needed to pay the refinance back, and flags a payment that is not lower.

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LTV (Loan-to-Value) Calculator

Divides the loan amount by the property value to give the LTV percentage, then reads it as conservative, standard, high risk or above usual lending policy.

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Debt-to-Income Ratio (DTI)

Calculate your debt-to-income ratio (DTI): total monthly payments divided by gross income. Lenders usually approve credit when it stays below 30%.

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IPTU Property Tax Estimator

Estimate the annual Brazilian property tax (IPTU) from the assessed value and the city tax rate. Find out how much you will pay and plan ahead.

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Cap Rate Calculator

Calculate the cap rate of a property by dividing annual net operating income by the price. Evaluate the return on real estate investments.

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Gross and Net Rental Yield

Enter monthly rent, property price and yearly costs: gross = rent·12/price and net = (rent·12 − costs)/price, both returned as percentages.

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Vacancy-Adjusted Rental Yield Calculator

Monthly rent, share of empty months and yearly costs against the purchase price: rent x 12 x (1 - vacancy) - costs, over price. 2000 at 8% on 350000 is 5.28%.

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Rental Property ROI Calculator

Monthly rent times 12 minus yearly costs, divided by down payment plus closing fees: the annual percent return on the cash actually put in.

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1% Rule Check for Rental Property

Enter monthly rent and purchase price to get the rent-to-price percentage and see whether the deal clears the 1% rule used to screen rentals.

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50% Rule for Rental Expenses

Applies the 50% rule to a monthly rent: half is assumed to go on upkeep, vacancy and management, and the remainder is shown as monthly net operating income.

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Outstanding Loan Balance at Month m (Fixed Payment)

Give the financed amount, monthly rate, term and month m for the balance PV(1+i)^m − PMT·((1+i)^m − 1)/i, Brazil's Price amortization.

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Total Interest Paid Calculator

Find out how much you pay in interest alone over a loan with the French (Price) amortization. Enter the installment, the number of months and the amount financed.

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Tire Diameter Calculator for P and LT Sizes

Turns a marking like 205/55R16 into overall diameter in mm: width x aspect/100 x 2, plus rim inches x 25.4. That size comes to 631.9 mm.

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RPM to Speed Calculator

Calculate vehicle speed in km/h from engine RPM, final drive ratio and tire radius. Ideal for builds and mechanical tuning.

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Electric Car Range Calculator by kWh

Enter usable battery in kWh and consumption in kWh per 100 km to get driving range in km, since range = capacity ÷ consumption × 100.

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EV Charging Time Calculator

Divides the kWh you still need by the charger power in kW and adds a 10 percent loss margin: 40 kWh on an 11 kW wallbox takes about 4 hours.

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0-100 km/h Time from Power and Weight

Rule-of-thumb acceleration estimate in seconds from engine power in HP and kerb weight in kg: t = (kg/HP)^0.75 x 0.85. Not a track figure.

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Drag-Limited Top Speed from Horsepower

Engine power and frontal drag area Cd.A give the speed at which aerodynamic drag eats the whole output. A cube-root law: twice the power buys only 26% more.

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Braking Distance Calculator (Physics)

Speed in km/h and a friction coefficient give the skid distance in meters by v² / (2 · μ · 9.81). Reaction distance is not part of the result.

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Hydroplaning Speed Calculator

Enter tire pressure in PSI and get the critical km/h at which tires ride on water: the NASA rule 10.35 * sqrt(PSI) gives mph, times 1.609. 32 PSI is 94.2.

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Trip Fuel Cost Calculator

Calculate the fuel cost of a trip from the distance, your car mileage (km/L) and the price per liter. Plan the budget for your next road trip.

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Next Oil Change Mileage

Adds the interval of your oil type to the current odometer reading: 5,000 km for mineral, 7,500 km for semi-synthetic, 10,000 km for full synthetic.

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Annual Car Depreciation Calculator

Applies a fixed yearly depreciation rate to a purchase price and returns the residual value of the car after N years, following value x (1 - d) raised to years.

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Tire Tread Wear and Remaining Life in km

Enter the current tread depth, the minimum you accept and the wear per 10,000 km to get the distance left. 5 mm, 1.6 mm and 1 mm give 34,000 km.

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Recommended Octane by Compression Ratio

Type the engine compression ratio and get the minimum octane band: below 9 takes 87, up to 10.5 takes 89-91, up to 12 takes 91-95, above that 95-98.

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Engine Redline RPM Estimator by Displacement

Rough rule of thumb from engine size in cc: 11000 - cc/2.5. It reads high for street cars, so treat the number as an upper bound, not a factory spec.

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Tire Circumference Calculator (205/55 R16)

Section width, aspect ratio and rim in inches give the rolling distance in mm: pi x (2 x sidewall height + rim x 25.4). A 205/55 R16 covers 1985 mm per turn.

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Power-to-Weight Ratio Calculator (kg/HP)

Weight in kg divided by engine output in HP: 12 is an economy car, 8 a hot hatch, 4 to 6 a sports car, near 1 a Formula 1. Lower means quicker.

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Fuel Tank Range Calculator

Calculate your car driving range on a full tank by multiplying the capacity (in liters) by the average fuel economy (km/L). Plan trips and fuel stops.

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Time Zone Overlap Finder

Find the overlapping working hours between two time zones to schedule meetings. Ideal for remote work and teams spread across different countries.

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Flight Distance (Haversine Formula)

Enter origin and destination latitude and longitude in degrees for the great-circle distance in km, taking Earth's mean radius as 6371 km.

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Trip Cost Split Calculator

Takes the total spend and the number of travelers and returns the equal share each one owes; it does not track who already paid for what.

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Jet Lag Recovery Calculator

Estimate how many days your body needs to adjust to jet lag after a trip, using the rule of thumb of about one day per time zone crossed.

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Travel Clothes Packing Calculator

Turns trip days into a packing list at 1 t-shirt, 0.5 pants and 1.1 underwear per day, rounded up: a 7 day trip gives 7 shirts, 4 pants and 8 underwear.

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Daily Travel Budget by Country Cost Tier

Pick how pricey the destination is and how you travel to get a reference USD figure per day, from 25 for backpacking on the cheap up to 500 for luxury.

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Driver Fatigue Calculator by Hours Driven

Enter hours at the wheel for break advice: up to 2 h is safe, 2 to 4 h a 15 min stop, 4 to 6 h a 30 min stop, over 6 h mandatory rest.

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Trip CO2 Emissions by Transport Mode

Multiplies trip distance in km by the mode factor (car 0.19, plane 0.25, bus 0.07, train 0.04 kg per km) and returns total kilograms of CO2.

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Daylight Hours by Latitude and Day of Year

Turns a latitude and a day number from 1 to 365 into hours of daylight using the CBM sunrise model: 10.7 hours at 23.5 S on day 172.

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Sunrise and Sunset Time Estimator by Latitude

Latitude and day of the year feed the solar declination and hour angle for an approximate pair of times in solar hours. No longitude or time zone correction.

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Airport Check-in Arrival Time

Suggests how many hours ahead of departure to reach the airport: 1.5 for a domestic flight, 3 for international, plus 30 minutes if you check a bag.

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Flight Time by Cruise Speed

Takes the distance in km and the km/h flown, adds 0.5 h of taxi and ground margin, and returns the hours in the air: 3000 km at 850 km/h gives 4.03.

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Altitude Acclimatization Time Calculator

Target elevation in meters returns the minimum days to acclimatize: one extra day for every 300 m gained above 2500 m, and zero below that mark.

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Depth of Field (DOF) Calculator

Focal length in mm, f-number, subject distance in m and circle of confusion in mm return the total in-focus range in meters, from the hyperfocal formula.

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Hyperfocal Distance Calculator

Calculate the hyperfocal distance of your lens from focal length, aperture and circle of confusion. Maximize depth of field in your photos.

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Sunny 16 Rule Calculator

Gives the shutter speed for bright sunlight from film or sensor ISO, starting at 1/ISO second at f/16 and rescaling for whatever aperture you pick.

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Exposure Value (EV)

Enter aperture f-number, shutter speed in seconds and ISO to get EV = log2(N²/t) − log2(ISO/100), a single number for the light in the scene.