100+ Free Online Calculators
for everything you calculate.

Calculate your monthly mortgage payment, total interest, and full amortization schedule for any home loan.

Estimate monthly payments and total interest for any fixed-rate loan.

Calculate auto loan payments with car price, trade-in, sales tax, fees, and APR — see total cost and interest.

See how investments grow over time with compound interest and regular contributions.

Estimate whether you're on track to retire — see your nest egg at retirement age.

Free ROI calculator — compute return on investment %, net profit and annualized ROI over any holding period. Instant results with formulas and examples.

Calculate sale price after applying a discount percentage.

Calculate Customer Acquisition Cost from marketing and sales spend.

Calculate Customer Lifetime Value. Project total revenue per customer to guide acquisition spend and retention.

Body Mass Index — weight-to-height ratio. Get category ranges and a quick health snapshot from height and weight.

Basal Metabolic Rate — calories burned at rest. Uses Mifflin-St Jeor for accurate resting calorie needs.

Total Daily Energy Expenditure. Combine BMR with activity level to plan cutting, bulking or maintenance.

Daily calorie needs from age, sex, weight, height, activity and goal (Mifflin-St Jeor).

Free running pace calculator — get pace per km and per mile, and predicted finish times for 5K, 10K, half marathon and marathon.

Calculate percentages, percentage of, and percentage change.

Free online scientific calculator with trig functions, logarithms, powers, roots and constants. No signup, instant results.

Free slope calculator: find the slope of a line from two points, plus rise over run, angle, distance and the y = mx + b equation.

Free grade calculator — compute weighted class grade from assignments, tests and exams, plus the score you need on the final to reach a target grade.

Find your exact age in years, months, weeks, days, hours and minutes from a birth date to any target date.

Format, validate and beautify JSON. Pretty-print, minify and spot syntax errors in API responses.

Encode text to Base64 and decode back. Handles Unicode and URL-safe variants for developers and QA.

Generate v4 UUIDs. Generate one or many random identifiers for databases and APIs.

Convert Unix timestamp to date and vice versa. Free online tool with instant results, formulas and worked examples.

Generate a QR code for any text or URL. Great for links, WiFi, contact cards and offline sharing.

Generate strong random passwords. Choose length and character sets for accounts, keys and Wi‑Fi.

Estimate monthly AI API costs across OpenAI, Anthropic, Google and open models by tokens and request volume.

Calculate OpenAI API spend for GPT-4o, GPT-4o mini, GPT-4 Turbo, o1 and GPT-3.5 by tokens and request volume.

Convert token counts and per-million-token prices into dollar cost per request, per day and per month.

Estimate ChatGPT API costs for building a chatbot — includes conversation history, system prompts and monthly volume.

Estimate monthly GitHub Actions spend by runner OS, workflow minutes, jobs and included free tier.

Calculate monthly API spend by requests, cost per 1,000 calls, data transfer and free tier.

Compare monthly cloud VM costs across AWS, Azure and GCP with storage, egress and reserved-instance discounts.

Quantify the revenue, wage and SLA cost of outages by minutes down, revenue rate and affected staff.

Find your true freelance hourly and day rate from target salary, expenses, taxes and billable hours.

See the true monthly, yearly and 5-year cost of a SaaS or subscription — with seats, price hikes and trial periods.

Estimate total project cost from labor hours, materials, overhead, contingency and profit margin.

Convert salary and target income to hourly, daily, weekly and monthly rates — with taxes and PTO.

Estimate the USD cost of any Ethereum transaction from gas price (gwei), gas limit and ETH price.

Project staking income across ETH, SOL, ADA and other proof-of-stake assets using APR, compounding and price change.

See what a dollar-cost averaging plan would have returned — enter buy size, frequency and start date.

Calculate profit, fees and ROI on a crypto trade from buy price, sell price and position size.

Compute blended and paid CAC from marketing spend, sales headcount cost and new customers acquired.

Estimate customer lifetime value from ARPA, gross margin and monthly churn, with LTV:CAC comparison.

Convert between MRR and ARR, project growth, and see quick-ratio and net new MRR from movement inputs.

Compute customer and revenue churn, retention rate, and average customer lifetime from monthly numbers.

Estimate YouTube ad revenue from views, CPM, RPM and niche — plus sponsorship-equivalent income.

Model the return on an SEO investment from traffic, conversion rate, order value and content cost.

Calculate email campaign revenue and ROI from list size, deliverability, open rate, CTR and conversion.

Convert word count into reading time for any audience — supports fast, average and technical reading speeds.