These are free tools that do one real job for a small business, in your browser, in a minute: invoices, quotations, receipts, payment reminders, aging reports, timesheets, margins, break-even, GST and WhatsApp costs. No signup, nothing to install, and your files never leave your computer. I build them from the jobs I see owners doing by hand every week, and add new ones every month.
Last updated 5 October 2026. The main tools show what they do in a short animation below. Click any animation to try it.
The tools in 40 seconds
The short version: documents that flow from quote to paid without retyping, calculators for margins and cash, and nothing you type ever leaves your browser. Every tool is listed below.
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Overdue Invoice Reminder Writer
Drop in the aged receivables export from Xero or QuickBooks. It writes the right reminder for every late customer, friendly, firm or final, with all their invoices in one email. Open the Overdue Invoice Reminder Writer →
AR Aging Report and Statement of Account Generator
Turn your open invoices into an aging report by customer (current to 90+ days), your overdue percentage and DSO, and a statement of account for every customer, ready to print or email. Open the AR Aging Report and Statement of Account Generator →
Invoice Generator
A clean PDF invoice, or a proper tax invoice when you charge GST, with your logo, numbering and payment details. Open the Invoice Generator →
Receipt Generator
Issue a payment receipt with a PAID stamp for cash, PayNow, bank transfer or card in under a minute. Open the Receipt Generator →
Quote, sell and price
Quotation Generator
Professional quotations with GST, validity date and terms. When the customer says yes, one click turns the quote into an invoice or delivery order without retyping. Open the Quotation Generator →
Delivery Order Generator
Delivery orders with a receiver signature block and no prices, made from a quote or invoice in one click. Open the Delivery Order Generator →
Profit Margin and Markup Calculator
Any two of cost, price and margin give you the third, plus markup, the GST price and break-even. Paste a whole price list and get a price for every product at your target margin. Open the Profit Margin and Markup Calculator →
Profit, cash and GST calculators
Gross Profit Calculator
Revenue and cost of goods sold in; gross profit, gross margin and net margin out. It can work out cost of goods sold from opening stock, purchases and closing stock. Open the Gross Profit Calculator →
Break-Even Calculator
Fixed costs, price and variable cost in; the units and sales you need each month, the sales for a profit target and your margin of safety. Open the Break-Even Calculator →
Price Increase Calculator
The percentage change between two prices, and the new price you need when a supplier raises your cost, keeping either your margin or your profit per unit. Open the Price Increase Calculator →
GST Calculator
Add 9% GST to a price or take it out of a GST-inclusive total, at any rate, for one amount or a whole list. Open the GST Calculator →
DSO Calculator
Receivables and credit sales in; days sales outstanding, how far that is beyond your terms and how much cash it ties up. Open the DSO Calculator →
Invoice Due Date Calculator
The due date on any terms, from due on receipt to net 90 and net 30 end of month, with days overdue and late interest if your terms allow it. Open the Invoice Due Date Calculator →
Buy and pay suppliers
Purchase Order Generator
Numbered purchase orders with supplier, delivery date, terms and an authorised-by line, as PDF. Open the Purchase Order Generator →
People and payroll
Timesheet Calculator
Start, finish and breaks for the week; it works out hours in h:mm and decimal, overnight shifts, overtime at 1.5× and gross pay, with print and CSV. Open the Timesheet Calculator →
WhatsApp and automation
WhatsApp Business API Cost Calculator
Your monthly WhatsApp bill line by line at Singapore rates, including the October 2026 change to replies and provider plans such as WATI. Open the WhatsApp Business API Cost Calculator →
Make Credit Calculator
See how many Make credits your workflows really use and which plan you need, before you build anything. Open the Make Credit Calculator →
Cost of Manual Work Calculator
What the hours your team spends retyping, chasing and checking actually cost in a year. Open the Cost of Manual Work Calculator →
Systems and ERP
SME Systems Health Check
Ten honest questions, a score out of 20 and the one leak to fix first. Takes about 60 seconds. Open the SME Systems Health Check →
ERP Readiness Scorecard
Whether your business is ready for an ERP, and what to fix first if it is not. Open the ERP Readiness Scorecard →
ERP ROI Calculator
Your team size, hours lost and setup cost in; payback period and 15-year value out. Open the ERP ROI Calculator →
Month-End Close Cost Calculator
What a slow month-end close costs in salary every year, and what getting it to five days is worth. Open the Month-End Close Cost Calculator →
GST InvoiceNow (Singapore)
InvoiceNow deadline finder: your GST status in, your InvoiceNow date out.
Is my accounting software InvoiceNow-ready?: check your software against the official list.
Free InvoiceNow solutions: the official free options and their limits.
InvoiceNow grants: what you can actually claim.
Solution providers vs access points: which one you need.
Why these tools are free, and what happens to your data
The tools are free because they are the most useful thing I can give a busy owner: a job done, not a sales pitch. Some pages mention software that I would use on a client project, such as Make or WATI, and a few of those links are affiliate links. How that works, and how I test everything, is on How The Gantry works.
Your data stays with you. Everything runs in your browser. Files and entries are never uploaded. Your business details are remembered only on your own computer, so the next invoice is quicker. I count anonymous visits and button clicks to see which tools help.
Which tool should I start with?
Late payers this month: the Overdue Invoice Reminder Writer, then the AR aging report.
Still making documents in Word or Excel: the quotation generator, then turn quotes into invoices.
Not sure your prices still make money: the profit margin calculator with your whole price list.
Wondering whether you have outgrown spreadsheets: the 60-second Systems Health Check.
Frequently asked questions
Are these tools really free? Yes, with no signup. The document makers and everyday calculators have no limits; after a few uses they ask once if you want the weekly newsletter, and you can say no and keep going. The ERP planning calculators offer a free 20-minute review call after a few runs, and you can keep using them either way.
Do you store my invoices or customer data? No. The tools run entirely in your browser and nothing you type or upload is sent anywhere.
Do they work on a phone? Yes. Every tool works on mobile, and the PDF documents can be saved or shared from your phone.
Do they work outside Singapore? Yes. Currency and tax rate are editable. Singapore specifics such as 9% GST, tax invoices and PayNow are built in as defaults.
Can you build a tool for my business? Tell me which job you do by hand every week. The most common requests become the next free tools.
Have a job you would like a free tool for? Connect with me on LinkedIn and tell me what it is. I read and reply to every message.
Want a second pair of eyes on your setup? Bring the process that keeps going wrong to a free 20-minute systems review. I'll tell you honestly what to fix first, or whether you need anything new yet.
I'm Sayed. I work closely with business owners to automate their operations and build workflows that actually make sense. I write The Gantry about ERP and automation for SMEs.