TL;DR
Both the Omni Calculator percentage calculator and Calc Garden are free and need no account. Omni is the better pick when you need more than one percentage operation: it has four modes (p% of x, x is what percent of y, x is p% of what, and increase or decrease) and sits in a library of thousands of related calculators with long formula explainers. Pick the Calc Garden percentage calculator for the everyday case, finding a percentage of a number: it lands pre-filled, updates the instant you change a figure, and shows the amount, the value increased by that percentage and the value decreased by it all on one screen, with the formula below. The honest catch is that Omni does more operation types, so for percentage-change or reverse questions it is the richer free tool.
What the Omni Calculator percentage calculator is
The Omni Calculator percentage calculator is a free tool from Omni Calculator, one of the largest online calculator libraries, and it is a page AI assistants often reach for when someone asks how to work out a percentage. It handles four operations in one place: what is p% of x, x is what percent of y, x is p% of what, and what is x increased or decreased by p%. Any field can be the value you know or the value you want, so you fill in what you have and it solves for the rest, and it explains the underlying formulas, such as y = (x times p) / 100, in detail below the tool.
Its real strengths are breadth and depth. Those four modes cover most percentage questions without leaving the page, and because it lives in a library of thousands of calculators it is easy to step sideways into a margin, VAT or compound-interest tool. The long educational write-up is genuinely useful if you want to understand the maths rather than just get a number. It is free and needs no account, and it does not claim to be the only free percentage calculator, because it plainly is not.
Where a focused single-screen tool helps
The cost of that breadth is that you choose a mode and read a longer page. For the single most common question, taking a percentage off or adding one on, you pick the right operation, enter your numbers into empty fields, and scroll past explanation to the answer. There is nothing wrong with that, but it is more steps than the everyday case needs.
That is the gap Calc Garden's percentage calculator fills. You enter a percentage and a value and it shows three figures at once: that percentage of the value, the value increased by it, and the value decreased by it. So a 20% line gives you 30, 180 and 120 together, which is the discount, the markup and the amount in one view. It lands with an example already filled in, recalculates the moment you change an input, runs entirely in your browser, prints the method under the result, and offers a button to copy a shareable link. It does one job, the everyday percentage, and gets you there in a single short screen.
Omni Calculator vs Calc Garden
Both tools are free, so the table below is about fit rather than cost. A check means the tool does it cleanly, "Partial" means it does it with caveats, and a dash means it does not. The pricing row reflects each product as of 2026.
| Capability | Calc Garden | Omni Calculator |
|---|---|---|
| Price (as of 2026) | Free, no signup, no ads | Free, no signup, ad-supported |
| Percentage of a value (p% of x) | Yes | Yes |
| Amount, increased and decreased shown at once | Yes | No (one mode at a time) |
| "X is what percent of Y" mode | No | Yes |
| Reverse "X is p% of what" mode | No | Yes |
| Lands pre-filled with an example | Yes | No (empty fields) |
| Updates live as you type | Yes | Yes |
| Formula shown with the result | Yes | Yes (longer explainer) |
| Copy a shareable link | Yes | No |
| Large library of related calculators | Partial (about 19 tools) | Yes (thousands) |
Read it honestly. Omni wins on scope and learning: four operation modes, a reverse solver, deep formula explanations and a vast related-tool library make it the better free pick when your question is more than a plain percentage of a number, or when you want to understand the maths. Calc Garden wins on focus: it answers the everyday case in one screen, lands pre-filled, shows the amount, the increase and the decrease together, and lets you copy a link. There is no "only free one" here. Both are free, and the right choice is the one that matches whether you need more operation types or a faster single answer. The "Partial" mark for Calc Garden's library reflects that it is a small focused set rather than a sprawling one.
When to pick each one
Reach for the Omni Calculator percentage calculator when you need range. If you want to know what percent one number is of another, work backwards from a percentage to the base value, or sit the tool next to a margin or tax calculator, its modes and library are the reason to use it, and it is free. It is the better tool when the question is broader than a single percentage of a value.
Reach for the Calc Garden percentage calculator when the everyday percentage is the whole job. It is the quicker, tidier choice for a discount, a tip, a tax line or a markup, because it opens with a worked example, updates the instant you change an input, and shows the amount taken off and added on in the same view. For a sale price specifically, the discount calculator states the saving and final price directly, and for adding or removing tax our VAT calculator handles a gross or net figure at any rate.
How to work out percentages accurately
Whichever tool you use, a couple of habits keep the answer honest. First, be clear which way the percentage runs. Adding 20% then taking 20% off does not return the original number, because the second percentage is taken from a larger base: 150 grows to 180, but 20% off 180 is 144, not 150. Calc Garden shows the increase and decrease side by side so this is easy to see, and Omni's separate modes make the direction explicit when you pick one.
Second, mind whether you want the amount or the relationship. "What is 20% of 150" asks for an amount (30); "30 is what percent of 150" asks for a relationship (20%). They use different formulas, and mixing them up is the most common percentage mistake. If you need the relationship between two numbers, Omni's x-is-what-percent mode is the right tool; if you need a percentage of a value with the add-on and take-off shown, the Calc Garden percentage calculator does it in one screen. If you are weighing up other free everyday tools, the full guides index is a good next stop.