Free Tools for Mercari & Yahoo Auctions

Everything you need for selling on Japanese flea market apps.
All tools are free and require no registration.

Calculators

Profit, fees & shipping costs

Profit Calculator

Calculate net profit after platform fees and shipping costs.

Fee Comparison

Compare fees across Mercari, Yahoo Auctions, Rakuma & PayPay.

Shipping Calculator

Find the cheapest shipping method based on size and weight.

ROI Calculator

Calculate return on investment for reselling. Includes hourly wage.

Tax Calculator

Estimate taxes on flea market income in Japan.

Listing Tools

Descriptions & templates

Template Generator

Generate SEO-optimized product descriptions by category.

Title Generator

Create product titles that sell. Optimized for search.

Hashtag Generator

Get hashtag suggestions for better discoverability.

Prohibited Word Checker

Check for banned words before listing.

Image Tools

Edit product photos

Image Resize & Compress

Resize to platform specs & reduce file size.

Watermark Tool

Add watermarks to protect your photos from theft.

Square Crop

Crop photos to square format for flea market apps.

Photo Grid

Combine multiple photos into one image.

Safety Tools

Fake detection & condition check

Fake Item Checker

Authentication tips for checking brand items.

Condition Checker

Objectively evaluate and grade item condition.

Management Tools

Packing & sales tracking

Packing Guide

Get packing material and shipping method recommendations.

Sales Tracker

Track sales, purchases, and profits.

💡 All tools are completely free

No registration required. Add to your home screen for quick access like an app. All calculations are done on your device - no data is sent to servers.