Short answer
Export your products as a CSV from Shopify, change the Variant Price column (and Compare At Price if you use it) and import the file with Overwrite existing products ticked. The free Shopify bulk price editor on this site changes prices by percent or amount, rounds them and shows a preview, all in your browser. Always keep a backup and import a small batch first.
Free tools for this
Export and keep a backup
In Shopify admin open Products, choose Export and download all products as a CSV. Save an untouched copy. If anything goes wrong, importing that copy puts the old prices back.
Decide the rule
A flat percentage is simplest, but think about margin first. Raising every price by 10 percent does not help if your shipping and ad costs rose by more. Change only the products or tags that need it, and leave loss leaders alone.
Try it now: Shopify Bulk Price Editor → · Shopify Profit Margin and Fees Calculator →
Round to a price style
Prices that end in 99 or 9 are common in India and keep numbers tidy. A calculated price of 1234 becomes 1199, the nearest price ending in 99. Choose one style for the whole store so prices look consistent.
Compare-at prices
The compare-at price is the higher price shown crossed out. Use it only for real previous prices. Setting it to a percentage above every price to fake a sale is misleading and can break consumer rules.
Import safely
Import a small batch of 5 to 10 products first with Overwrite existing products ticked, then open them and check prices and compare-at prices. Then import the rest. Check the live store, the cart and a test checkout.
Check what else uses the price
Feeds for Google Shopping and ads, discount codes, bundles and apps may use or copy prices. After a bulk change confirm they updated, and let your ad accounts see the new prices.