Guides and how-tos
Short, practical answers to the questions that come up when you use our tools — with worked examples and the formulas behind them.
Latest guides
- Guide · EducationThe 12 Best AI Course Creators in 2026, Compared by What They Actually DoAI course generators, course platforms, video tools and corporate authoring compared: what each AI creates, real prices, free plans and the hidden fees to check.Oct 11, 2026 · 16 min read
- Guide · PDFHow to Make a Professional PDF From Plain Text (Free)The typesetting rules that make a document look professional, and a free way to apply them: paste text, get a designed PDF, then fine-tune any page visually.Oct 9, 2026 · 8 min read
- Guide · Date & TimeHow Long Is 3–5 Business Days? Charts for Every Common Range3–5 business days is 3 to 7 calendar days. See exactly when 2–8, 5–7, 7–10 and 10–15 business days end for every order day, and how holidays shift them.Oct 8, 2026 · 7 min read
- Guide · EducationWhat Is 18 Out of 30 as a Grade? Test Score to Percentage Charts18/30 is 60%, a D−. Score-to-percentage and letter-grade charts for tests out of 10, 20, 25, 30, 40 and 50 — plus the rounding rule that turns a B into a B+.Oct 8, 2026 · 6 min read
- Guide · CalculatorsHow to Calculate Percent Savings (and Why 30% + 20% Isn't 50%)The percent savings formula with real examples, plus stacked discounts, dollar vs percent coupons, buy-one-get-one deals, bulk packs and annual plans.Oct 8, 2026 · 6 min read
- Guide · EducationWhat Grade Do I Need on My Final? The Formula, ExplainedWork out the exact final exam score you need for the grade you want, with worked examples, weighted and points-based classes, and syllabus rules that change the answer.Oct 8, 2026 · 6 min read
Education
- Guide · EducationThe 12 Best AI Course Creators in 2026, Compared by What They Actually DoAI course generators, course platforms, video tools and corporate authoring compared: what each AI creates, real prices, free plans and the hidden fees to check.Oct 11, 2026 · 16 min read
- Guide · EducationWhat Is 18 Out of 30 as a Grade? Test Score to Percentage Charts18/30 is 60%, a D−. Score-to-percentage and letter-grade charts for tests out of 10, 20, 25, 30, 40 and 50 — plus the rounding rule that turns a B into a B+.Oct 8, 2026 · 6 min read
- Guide · EducationWhat Grade Do I Need on My Final? The Formula, ExplainedWork out the exact final exam score you need for the grade you want, with worked examples, weighted and points-based classes, and syllabus rules that change the answer.Oct 8, 2026 · 6 min read
- Guide · PDFHow to Make a Professional PDF From Plain Text (Free)The typesetting rules that make a document look professional, and a free way to apply them: paste text, get a designed PDF, then fine-tune any page visually.Oct 9, 2026 · 8 min read
- Guide · PDFHow to Sign a PDF Without Printing ItSign a PDF in a minute on a computer or phone: draw, type or upload your signature, add the date and download — plus when an electronic signature is legally enough.Oct 6, 2026 · 5 min read
- Guide · PDFHow to Merge PDF Files (Without Uploading Them Anywhere)Combine PDFs into one file on any device, privately. Plus how to fix the most common problems: wrong page order, huge files and password-protected PDFs.Oct 4, 2026 · 6 min read
- Guide · PDFHow to Convert PDF Pages to Images (JPG or PNG)Turn PDF pages into JPG or PNG images at the right resolution for screens, printing or social media — and when to choose PNG instead of JPG.Oct 4, 2026 · 6 min read
Date & Time
- Guide · Date & TimeHow Long Is 3–5 Business Days? Charts for Every Common Range3–5 business days is 3 to 7 calendar days. See exactly when 2–8, 5–7, 7–10 and 10–15 business days end for every order day, and how holidays shift them.Oct 8, 2026 · 7 min read
- Guide · Date & TimeHow to Calculate Business Days Between Two DatesCount working days by hand or in Excel, add business days to a deadline, and handle observed and substitute holidays — with 2026 working days per month for the US and UK.Oct 7, 2026 · 7 min read
Calculators
- Guide · CalculatorsHow to Calculate Percent Savings (and Why 30% + 20% Isn't 50%)The percent savings formula with real examples, plus stacked discounts, dollar vs percent coupons, buy-one-get-one deals, bulk packs and annual plans.Oct 8, 2026 · 6 min read
- Guide · CalculatorsHow to Solve Any Triangle: Which Rule to Use and WhenPick the right rule for what you know — law of cosines, law of sines or Pythagoras — with worked examples, the SSA ambiguous case and quick answer checks.Oct 7, 2026 · 8 min read
- Guide · CalculatorsHow to Find the nth Term of a SequenceStep-by-step methods for linear, quadratic and geometric sequences, how to tell which you have from the differences, and how to check whether a number is in the sequence.Oct 7, 2026 · 7 min read
- Guide · CalculatorsHow to Calculate Percentage Increase (and Decrease) — With ExamplesThe one formula for percentage increase and decrease, worked examples with prices and salaries, and the mistakes that trip people up — like percent vs percentage points.Oct 4, 2026 · 6 min read
Converters
Business
- Guide · BusinessHow to Write a Quotation That Wins the JobWhat to put in a quote, how to itemise prices, handle tax, set a validity date and deposit, and follow up — plus how a quote differs from an estimate.Oct 7, 2026 · 7 min read
- Guide · BusinessHow to Make an ATS-Friendly Resume That Still Reads WellWhat applicant tracking systems actually read, the formatting that trips them up, how to use job-advert keywords honestly, and bullet points that rank and persuade.Oct 6, 2026 · 7 min read
Images
- Guide · ImagesHow to Take a Passport Photo at Home (and Get It Accepted)Take a passport photo with your phone, crop it to your country's exact size and print a 4×6 sheet for a few cents — with the US, UK and Schengen rules.Oct 6, 2026 · 6 min read
- Guide · ImagesHow to Reduce an Image to 100 KB Without Losing Too Much QualityA practical method for getting photos under 100 KB — or any limit — while keeping them sharp: which settings to change first, and what to do when it still won't fit.Oct 4, 2026 · 7 min read
- Guide · ImagesHow to Prepare Photos and Signatures for Online Application FormsExam, visa, passport and job portals reject photos for size, dimensions or background. A checklist and step-by-step method to get accepted on the first upload.Oct 4, 2026 · 8 min read
- Guide · ImagesJPG vs PNG vs WebP: Which Image Format Should You Use?A plain-English comparison of JPG, PNG, WebP (and AVIF) with real file sizes, so you can pick the right format for photos, logos, screenshots and websites.Oct 4, 2026 · 7 min read
Developer
- Guide · DeveloperHow to Format JSON Correctly (and Fix the Errors That Break It)What valid JSON looks like, how to pretty-print and minify it, and how to fix the eight errors that cause most “Unexpected token” messages.Oct 4, 2026 · 8 min read
- Guide · DeveloperHow to Convert CSV to JSON (and Back) Without Breaking Your DataConvert spreadsheet data to JSON and JSON back to CSV correctly: quoted commas, line breaks inside cells, numbers vs text, nested objects and Excel quirks.Oct 4, 2026 · 7 min read
- Guide · DeveloperWhat Is a Unix Timestamp? Epoch Time ExplainedWhat Unix time is, why it starts in 1970, how to tell seconds from milliseconds, how time zones fit in, and how to convert timestamps in common languages.Oct 4, 2026 · 6 min read
Finance
- Guide · FinanceHow to Calculate Loan EMI (Monthly Payment) — Formula and ExamplesThe EMI formula in plain English, a worked example, why early payments are mostly interest, and how loan term and prepayments change what you pay.Oct 4, 2026 · 7 min read
- Guide · FinanceHow to Calculate Compound Interest (and How It Differs From Simple Interest)The compound interest formula with a worked example, how compounding frequency and monthly deposits change the result, and the rule of 72.Oct 4, 2026 · 7 min read
Text
- Guide · TextHow to Calculate Reading Time for an Article or SpeechThe words-per-minute numbers that actually hold up, how to estimate reading and speaking time, and how to show a “5 min read” label honestly.Oct 4, 2026 · 5 min read
- Guide · TextHow to Clean Up and Format Messy Text (From PDFs, Emails and Websites)Fix broken line breaks, double spaces, curly quotes, invisible characters and duplicate lines in text copied from PDFs, emails and web pages — in the right order.Oct 4, 2026 · 6 min read