ForHosting KIT · Developer Utilities

Tidal prism volume calculator

The tidal prism volume calculator estimates how much water enters or leaves an estuary between representative low-water and high-water levels.

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Run — free How it works & API

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Provide the basin surface area in square metres and the tidal range in metres, and it applies the standard first-order relationship P = A × R. The result is returned in cubic metres with the supplied values and formula, making it easy to check, document, or reuse in environmental screening, coastal engineering, and preliminary estuary studies.

What the tidal prism represents

A tidal prism is the volume of water exchanged by a tidal basin or estuary between low water and high water during a tidal cycle. It is a useful first measure of the scale of tidal flushing, because a larger exchanged volume can transport more salt, sediment, nutrients, contaminants, and suspended material through an inlet. This calculator uses the basin surface area and the vertical tidal range to estimate that volume. Surface area describes the horizontal footprint of water participating in the level change, while tidal range describes the difference between the selected low and high water levels. Multiplying square metres by metres produces cubic metres. The estimate is deliberately simple and transparent: it treats the basin like a planform area rising or falling uniformly through the specified range. That makes the result appropriate for quick comparisons, feasibility work, classroom calculations, and early project screening where a detailed hydrodynamic model is not yet justified. It should be interpreted as a geometric estimate rather than a complete simulation of circulation through the estuary mouth.

How to choose consistent inputs

Enter the estuary or tidal-basin surface area in square metres and the tidal range in metres. Both measurements should refer to the same study reach and a compatible tidal condition. For example, do not combine an area mapped only at low water with an unrelated extreme storm-tide range unless that scenario is intentionally being studied. A representative spring, neap, mean, or design tidal range may be used, but record which one you selected so the result remains interpretable. If the area is available in square kilometres, convert it to square metres by multiplying by one million before entering it. If the range is in centimetres, divide by one hundred to obtain metres. Zero is accepted and produces a zero prism; a negative surface area is rejected because physical basin area cannot be negative. Negative tidal range is also rejected because the calculator expects the positive magnitude of the water-level difference. Use finite numeric values without unit symbols in the fields, since the units are fixed by the published input contract.

Interpret the result and its limits

The returned tidal prism is P = A × R, expressed in cubic metres. Suppose a basin covers 2,500,000 square metres and the selected tidal range is 1.8 metres: the estimated exchanged volume is 4,500,000 cubic metres. This number is valuable for comparing basins or tidal scenarios when the same assumptions are applied, but it is not automatically the exact volume passing through a particular inlet. Real estuaries have sloping banks, intertidal flats, branching channels, storage wetlands, river inflow, evaporation, phase differences, and spatially varying water levels. Their wetted surface area can change substantially during a tide. Detailed design, navigation studies, flood analysis, or ecological impact assessment may therefore require bathymetric integration, observed water levels, current measurements, or a calibrated hydrodynamic model. Treat this calculator as a reproducible first-order estimate and state the area source, tidal datum, tidal statistic, and survey date alongside the result. API requests cost $0.002; the deterministic formula ensures identical inputs produce identical outputs.

What you can do with it

Screen an estuary restoration concept

Estimate the water volume associated with a proposed tidal range before commissioning detailed hydraulic modelling.

Compare tidal flushing scenarios

Apply different representative ranges to the same mapped basin area and compare first-order exchanged volumes consistently.

Document a coastal study assumption

Produce a transparent cubic-metre estimate with the source inputs and formula available for reports or calculation records.

FAQ

What formula does the calculator use?

It uses P = A × R, where P is tidal prism volume, A is basin surface area, and R is tidal range.

Which units should I enter?

Enter surface area in square metres and tidal range in metres. The returned tidal prism is in cubic metres.

Does it account for sloping banks or changing wetted area?

No. It assumes the supplied planform area changes level uniformly, so complex basin geometry requires a more detailed method.

Why does a negative surface area cause an error?

Physical surface area cannot be negative. The calculator rejects it instead of returning a misleading negative water volume.

How much does an API calculation cost?

Each API request costs $0.002. The calculation is deterministic and does not use an external model or network service.

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

POSThttps://api.kit.forhosting.com/earth/tidal-prism

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/earth/tidal-prism \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"surface_area":2500000,"tidal_range":1.8}'

const res = await fetch("https://api.kit.forhosting.com/earth/tidal-prism", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "surface_area": 2500000,
    "tidal_range": 1.8
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/earth/tidal-prism",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "surface_area": 2500000,
    "tidal_range": 1.8
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/earth/tidal-prism", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"surface_area":2500000,"tidal_range":1.8}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"surface_area":2500000,"tidal_range":1.8}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/earth/tidal-prism", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "surface_area": 2500000,
  "tidal_range": 1.8
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "earth.tidal_prism",
  "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

Per request$0.002

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.

Read the full KIT documentation →