Dad's Calculator vs Fast Simple Invoice Maker
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Dad's Calculator
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Dad's Calculator is for the moment you reach for a calculator in your everyday life: the checkout line, the measuring tape, the stove. It keeps a notebook of everything you work out, adds up the lines you pick, and remembers them for next time. Right next to it: a unit converter, a recipe scaler and size charts. THE CALCULATOR • Every calculation stays in a notebook-style history. Your math, with receipts • Percent works the way you say it: 80 - 25% = 60 • Pick the lines you care about and get their sum, average, largest and smallest • Copy the result, or drop the sum straight into your next calculation • Name a set of lines (groceries, measurements, quotes) and save it for when your memory lets you down • Swipe a line away, or wipe the whole slate WITHIN ARM'S REACH • Converter: type one number, see every unit at once. Star the ones you use • Cooking: recipe for 4, dinner for 6? Change the servings, or match one ingredient, and the rest follows • Sizes: shoes and clothes in US / UK / EU / cm, because sizes never agree • Notebook by day, chalkboard by night. Switch anytime in Settings SECRET DIARY • Log measurements for each body part and your weight, in cm / inches and kg / lb • Compare with 1, 3 or 6 months ago, in a graph or a table
Fast Simple Invoice Maker
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Create polished invoices quickly—without needing an account. Fast Simple Invoice Maker keeps everyday invoicing simple, private, and available offline. CREATE AND SEND • Save clients and reuse their details • Add line items, taxes, discounts, notes, and payment terms • Choose professional invoice styles • Export print-ready PDFs • Share through Messages, WhatsApp, email, or Files OPTIONAL ONLINE INVOICES When you want an online workflow, sign in with Apple and publish selected invoices as private web links. Your client can open the link without creating an account. Use the secure web portal to review the invoices you chose to publish, and revoke a link whenever needed. OPTIONAL CARD PAYMENTS Connect your own Stripe account to offer secure card payment for the real-world goods or services on your invoice. Payment status and receipts stay connected to the invoice. Stripe is never required for creating, exporting, or sharing invoices. BUILT FOR REAL WORK • Continue creating, editing, saving, and exporting invoices offline • Keep local invoices on your device unless you explicitly publish them • Generate receipts for paid invoices • Use recurring invoice tools for repeat work • Work with supported currencies and invoice languages Fast Simple Invoice Maker helps freelancers, contractors, consultants, and small businesses move from finished work to a professional invoice—with fewer steps. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
Screenshots
Verdict
The clearest difference is in-app purchases: Dad's Calculator at none against Fast Simple Invoice Maker's 4. Dad's Calculator also leads on update cadence (every 2 days vs fortnightly) and iOS requirement (15.0 vs 18.2). On price, ads and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Fast Simple Invoice Maker sells 4 one-off in-app purchases. Dad's Calculator asks for nothing beyond the download.
Dad's Calculator ships an update every 2 days, Fast Simple Invoice Maker fortnightly. The most recent releases landed on November 3, 2026 and October 30, 2026 respectively.
| Parameter | Dad's Calculator | Fast Simple Invoice Maker |
|---|---|---|
| Price | Free | Free |
| Update frequency | Every 2 days — better | Fortnightly |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Devices | iPhone, iPad, iPod — better | iPhone, iPad |
| Requires iOS | 15.0 — better | 18.2 |
| Further details — not scored | ||
| Size | 31 MB | 11 MB |
| Age rating | 4+ | 4+ |
| Developer | Jaehun Kwon | Eric Savoie |
In-app purchases
Dad's Calculator
No in-app purchases
Fast Simple Invoice Maker
- Midnight Theme$0.49
- Forest Theme$0.49
- Warm Paper Theme$0.49
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- Theme - Ocean$0.49
Questions
Is Dad's Calculator free?
Is Fast Simple Invoice Maker free?
Do Dad's Calculator or Fast Simple Invoice Maker have ads?
Which is updated more often, Dad's Calculator or Fast Simple Invoice Maker?
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