Rent increase calculator
A 5% increase on a current rent of 1,500 adds 75, so the new rent is 1,575. Landlords get both lines for the renewal letter, and tenants can check a notice before replying. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Current rent
- 1,500
- Increase percent
- 5
- Increase amount
- 75
- New rent
- 1,575
A rent increase is the extra amount a tenant will pay after a landlord applies a percentage to the current rent. Landlords, property managers, tenants, and rent-review tools need both the new rent and the dollar increase before a lease letter, notice, or spreadsheet goes out. Zero percent is allowed and leaves the rent unchanged.
How a percentage rent increase becomes a new rent
A rent increase is a one-line identity: the new rent equals the current rent multiplied by one plus the increase percent divided by one hundred. Equivalently, the increase amount equals the current rent times the increase percent over one hundred, and the new rent is the current rent plus that extra amount. Five percent of one thousand five hundred is seventy-five, so the new rent is one thousand five hundred seventy-five.
Three and a half percent of one thousand two hundred forty-nine point nine nine is forty-three point seven four nine six five before rounding and forty-three point seven five after half-up to two decimals, so the new rent is one thousand two hundred ninety-three point seven four. Zero percent is a valid increase: the increase amount is zero and the new rent equals the current rent, which is useful when a lease letter restates an unchanged figure.
The calculator does not annualize a monthly figure, does not compound across several review years, does not apply statutory caps or rent-control ceilings, and does not convert currencies. You supply one current rent and one non-negative percent; it multiplies and adds, then returns the new rent as the primary result together with the increase amount so a notice can show both lines.
What you can do with it
Renewal letters and notices
Turn last year's current rent and a board-approved percent into the new rent and the extra dollars that belong on a renewal letter.
Tenant notice checks
Drop the posted current rent and the stated percent into two fields to verify the new rent before you reply to a raise.
FAQ
What happens if the percentage increase is negative?
A rent increase requires a percentage of zero or more; a negative percent would be a rent cut and is not billed.
How is the new rent rounded?
Inputs that are already finite numbers are echoed as parsed.
How do I calculate a rent increase by hand?
Multiply the current rent by the percentage and divide by 100 to get the increase. Add that amount to the current rent and you have the new rent, which is exactly what the calculator does.
Does it apply rent-control limits or legal caps?
No. It does not know statutory caps or rent-control ceilings where you live, so check the legal limit yourself before sending or accepting a new rent.
Can it work out increases over several years?
No. It handles one review at a time and does not compound across several years or turn a monthly figure into a yearly one. Run it again with the new rent for the next review.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/fin/rent-increase \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"current_rent":1500,"increase_percent":5}'const res = await fetch("https://api.kit.forhosting.com/fin/rent-increase", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"current_rent": 1500,
"increase_percent": 5
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/fin/rent-increase",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"current_rent": 1500,
"increase_percent": 5
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/fin/rent-increase", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"current_rent":1500,"increase_percent":5}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"current_rent":1500,"increase_percent":5}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/fin/rent-increase", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"current_rent": 1500,
"increase_percent": 5
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "fin.rent_increase",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
This rent increase calculator takes two finite numbers — current_rent in one currency and increase_percent as a percent, not a fraction — multiplies the current rent by one plus the percentage over one hundred, and returns the new rent together with the increase amount. A negative percentage is not an increase: the task fails with invalid_input instead of silently computing a rent cut.
How a percentage rent increase becomes a new rent
This rent increase calculator accepts two finite numbers — current_rent in one currency unit and increase_percent as a percent, not a decimal fraction — and returns both the increase_amount and the new_rent rounded half-up to two decimal places so goldens compare byte-for-byte across runtimes. A negative percentage is not an increase; it is a rent cut, and this capability rejects it with invalid_input rather than silently computing a lower rent. That distinction is the product: people searching for a rent increase calculator want the raised monthly or annual figure, not a general percent-change tool that also models decreases, discounts, or refunds.
Input contract, response shape, and error behaviour
Zero current rent and zero percent are allowed: the new rent is zero or unchanged rather than an error. Example: current rent one thousand five hundred and increase percent five yield increase amount seventy-five and new rent one thousand five hundred seventy-five. Keep both fields finite and pin the rounded money in tests so a notice generator and a script never disagree on the new rent. POST a JSON body with two required finite numbers. current_rent is the rent you already charge, in one currency, monthly or annual as long as you keep the same unit on the result; aliases rent, monthly_rent, old_rent, and current map to the same field so a worksheet can keep its column names. increase_percent is the raise as a percent of that current rent — five means five percent, not zero point zero five; aliases percent_increase, increase_pct, pct, and percentage are accepted. Each numeric field may arrive as a JSON number or a numeric string. Missing fields, empty strings, and non-finite values — NaN, Infinity, or text that does not parse as a number — fail with invalid_input naming the field. A negative current_rent fails because a rent amount cannot be below zero. A negative increase_percent fails with a message that a rent increase requires a percentage of zero or more; those failures are not billed. On success the body echoes current_rent and increase_percent, then reports increase_amount and new_rent rounded half-up to two decimal places, together with a formula string restating the identity. Pair the JSON with your own rule for whether the figure is monthly or yearly, because this endpoint does not convert periods, apply a local cap, or split a mid-year pro-rata.
Where a rent increase calculator earns its keep
Landlords and property managers use a rent increase calculator to turn last year's current rent and a board-approved percent into the figure that belongs on a renewal letter, including the extra dollars so the tenant can see the raise as an amount, not only a percent. Tenants and housing counselors drop the same two numbers in to check a notice before they reply. Failed validation does not consume balance. Keep both fields finite, pin the rounded new rent in tests, and you get a reproducible raised amount for notices, close checklists, and edge workers without standing up a property-management ledger of your own. The browser tool is free; the API path is the same algorithm billed at $0.002 per successful call so a worksheet and a script never disagree on the new rent.
Integration use cases
Portfolio and plugin automation
Pin new_rent in dashboards, LMS plugins, and CI fixtures from current_rent and increase_percent without a lease-accounting engine.
Technical questions
How do I calculate a rent increase from a percentage?
Send finite numbers current_rent (non-negative) and increase_percent (zero or more). The API returns new_rent = current_rent × (1 + increase_percent/100) and increase_amount = current_rent × increase_percent/100, both rounded half-up to two decimal places.
Does a zero percent increase fail?
No. Zero percent is a valid increase: increase_amount is zero and new_rent equals current_rent. Only a negative increase_percent is rejected.
What does the rent increase calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.